History
Eglinton West Subway - NDP started with shovels in ground 1994, Harris Conservatives cancelled 1995.
Spadina York Subway Extension - Liberals started 2006 - Successfully opened 2017.
Sheppard East LRT - Transit City - Miller/Liberals started 2009 with shovels in ground on early works was going to open by 2015, Rob Ford cancelled 2010.
Eglinton LRT - Transit City - Miller/Liberals bought tunnel machines 2010 - Under construction and expected to open in 2022.
Scarborough LRT - Transit City - City went through detailed engineering study and community meetings, detailed station layouts and elevations completed, Liberals committed to fund in full as extension of Crosstown. Rob Ford cancelled.in favour of a subway, then re-approved by Ford with condition of Crosstown not running at grade, then in 2012 Stintz/De Baeremaeker/Ford cancelled for a subway with less stops and $85 million in cancelled contracts.
Scarborough Subway Extension - Despite the decision having been made in 2012 to switch to the subway nothing is under construction. However, detailed engineering studies are complete, environmental studies are done with many revisions, and the RFP is issued but no contracts signed yet. Seems likely it will get built but this is pending contracts being signed.
Finch West LRT - Transit City - Miller almost started, Liberal budget constraints slowed, Rob Ford "cancelled"/delayed, Liberals signed contract in 2018 one month before Doug Ford's Conservatives took office - Under construction and expected to open in 2023.
Downtown Relief Line / Ontario Line - City/Liberals started as full metro which was underground with detailed engineering study. and community meetings on route assessments with route approved in 2016 and environmental assessment was underway in 2018, project delayed by Ford government with a new route and plan for using a light metro with above ground sections. RFP issued but no contracts signed yet. Seems likely it will get built but this is pending contracts being signed.
Proposed Form
Transit City - Build LRTs in the suburbs, and put them underground in denser areas.
Sheppard Subway - Build heavy metro under suburban streets between North York and SCC next to the 401 despite travel pattern analysis showing east-west travel on transit from SCC was less likely than north-south (i.e. towards downtown).
Scarborough LRT - Build LRT using much of the SRT footprint fully in its own right of way serving new areas such as Centennial College and Malvern.
Scarborough Subway - Build a heavy metro to Scarborough Town Center (later extended to Sheppard) with only 2-3 stops.
Downtown Relief Line - Build a heavy metro out of downtown Toronto to Pape with potential future extension towards Don Mills and Eglinton. Build underground to minimize impact on communities.
Ontario Line - Build a light metro through downtown from the CNE in the west to Don Mills and Eglinton in the east and have above ground portions.
Based on the information it seems like the Liberal / Miller / "Lefty" logic is to build based on expected capacity (i.e. heavy metro downtown), and environment (underground in denser areas, on the surface in the burbs for LRT). The Ford / Conservative / "Right Wing" logic is to build heavy metro in the burbs underground, and light metro into downtown.
Opinion Piece
It seems logical to me that (a) you plan based on needed capacity, (b) you build at grade when there isn't a big benefit of putting it elevated or underground in terms of travel time and the ridership wouldn't justify the cost, (c) you build underground to minimize impacts to existing communities, and (d) you build to handle growth or you build cheap to minimize regrettable spend when you later build for growth.
Transit City - A sensible plan. Building at the surface minimizes regrettable spend if there are future phases to have the LRT duck under main intersections or get fully buried. Seems much like the Brussels pre-metro where tunnels were served with trams/LRT originally with the routes running on the surface in the outskirts, but was converted in many places to full metro as it was needed. If anti-LRT / pro-subway wrenches hadn't been thrown into this plan we would be welcoming many more line openings around now.
Sheppard Subway - Not cost effective. Should be LRT mostly at grade. Now that the subway is built it should probably be reverted to pre-metro and extended to make it more useful. As a Fairview Mall shuttle it doesn't benefit enough people. YRT tried to funnel people into the line at Don Mills from Markham but that experiment failed as it was more convenient to take the bus on the 407 to Finch.
Scarborough LRT - A sensible plan. Serves new areas, scaled appropriately, good connectivity with Eglinton LRT.
Scarborough Subway - A partially sensible plan when ending at Scarborough Centre. Ending at Scarborough would terminate an existing heavy metro at a more natural transfer point to other modes (i.e. terminates the line at an actual destination). The downfall is comparing this option to the areas served by competing LRT plan (which really could/should still be built in the future). Not sensible is extending the line to Sheppard as that doesn't improve connectivity (i.e. routes are going to dump people at Sheppard to get on the line to go one station to Scarborough Center (the destination) where many other routes including the Durham BRT and GO will connect. This is going to lead to needless transfers and one stop trips and spends money that would be better spent elsewhere.
Downtown Relief Line - A sensible plan which puts the greatest carrying capacity into a route that in the future is likely to need it.
Ontario Line - Mostly sensible plan. I share the concern that this plan popped out of thin air but Metrolinx has been working through design and has come up with something mostly sensible. For line routing the plan seems sensible and line completeness is excellent with it serving a much greater area. Could have used the original route to minimize delay and get construction started. Running the line in the GO corridor at grade seems affordable although the routing to get the tunnels aligned to the corridor is more complex and may not actually save much. I don't understand the complaints from Leslieville residents on the line being above ground (i.e. at grade in the corridor) considering there is heavy diesel passenger rail in the corridor which would obviously be far louder. They should ensure running on opposite sides of the corridor taking corridor space doesn't constrain future GO/VIA expansion. Cross platform transfers at West Harbour are a good design feature. They should be choosing the highest capacity metro option since this will be the most utilized route as it makes no sense to build heavy metro in the suburbs while building light metro in the most dense area in the city. Some elevated route segments seem ill advised if the equipment was heavy metro but light metro should lessen the impacts.