There is a height clearance at the Toronto West Diamond to the point the hanger will be on top of the brace beams and the overhead will be hung from them.
As pointed out above, Metrolinx has known since 2009/2010 they had height clearance issues at Union Station and other places that I know of and no real surprise other than cost and time to fix them. I think Metrolinx wanted to do something different and been told they can't.
To dig down and lower the tracks is not that easy since there is very little material that can be removed before you hit concrete slab. You could dig out the track area and bolt the rails to the concrete slab, lowering the rail by haft the thickness of the ties or more depending on the location. You got the Simcoe, York, Bay and Yonge St underpass to deal with and that your base level. NOTE: If tracks lower, all the accessibility platforms will have to be rebuilt for the correct new height unless to be on a slope between the coach and platform.
You can raise the existing roof by cutting the support columns and jacking it up to add the extra material that is needed to get the clearness.
What I original wrote and after looking at the photo below shot on Jan 23, I had to rewrite this. Before you can touch the support columns, you have to cut the rivets from the arch frames as well brace the columns that will take platform space. You have to remove 3 arches over 6 tracks before you can deal with raising the first 2 rows of columns per arch for the first 2 tracks. At the same time, you need to remove the support trusses running east-west between the columns for the first 2 rows of columns. At this point, someone must have had decided to either removed the columns to cut them to splice the extension to it or to fabricate new columns to the correct height as well drilling new holes in them to match the trusses and the arches connections. You need to added angle material to the ends of the arch and truss so they can be bolted to the columns to give the similar look that exist today.
Once you have the first 2 tracks done and brace, you remove the arches and trusses for 4 more tracks that haven't been removed. You then can repeat the first operation for the next 2 tracks and then moved on to the next 2 before removing anymore trusses and arches. All the other existing braces will have to be removed and modify before reinstalling them. This will not be cheap to do.
This will push the roof completion back by 2 years.
As noted, you can run a gutter pan under the existing arches like TTC does at underpasses that will be faster and cheaper to do.