So to summarize.................GO Rex is the same as Melbourne and Sydney's CityRail system?
Depends if you compare the now or the future.
We just had a big ol' info dump last week when Public Transport Victoria did the public release of its heavy-rail plan/stragegy that it's effectively had in use for 4-5 years last week.
Melbourne's network - if the following plan is more or less implemented (no funding commitments yet, surprise surprise!) - the distinction between commuter rail and metro will become even more blurred and the two distinctions rendered obsolete.
Gweed's concept with everything converging on Union station is what Melbourne's (and to an extent Sydney's) system is trying to break. At present all trains in Melbourne terminate/originate at Flinders Street, some lines now run straight through. But new projects like the Melbourne Metro Tunnel, and reconfiguring the loop later on (see links below) will completely break this concept.
There's surely some way you can do the same thing in Toronto, but not making it centric on one major station, cos you might find you'll be in the position we're in now in a few decades.
Anyhow, background/explanation:
Current config/planned changes: Lines are currently grouped and over 15-20 years they'll be made into individual lines, summary:
(video accompanied the release of the doco)
Current config:
Ultimate / end of plan configuration:
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^ context: Pakenham (south east of city) is 62km, and Melton (other end of the line / one of the branches in the line that will be created by the Metro Tunnel project) is 45km from the CBD - i.e an over 100km train line that's likely to run on high frequencies (about 75-80km of it will be the combined peak frequencies of those branches).
"Grovedale" in that is an outer suburb of Geelong - an entirely separate city (basically Melbourne's Hamilton).
All the main doco here:
http://ptv.vic.gov.au/news/news-promotions/network-development-plan-metropolitan-rail/
Also put all the main images from the doco in a chronological order (over the different phase's projects) on UrbMelb, might make it easier to understand if you dont want to read slabs of text:
https://www.urban.com.au/forum/ptvs-network-development-plan-for-metropolitan-rail