I think Line 4 will be the last new heavy rail line. If we ever build another new line (that is not LRT), its probably gonna be a light metro like the Ontario Line. Interoperability will come with more and more lines like this. Would you ever envision Line 4 in it's current state extending along this ALRT route?
I believe the final configuration of Line 4 is most likely to be Sheppard West Station on Line 1 to McCowan Station on the SSE.
I find it highly improbable it will extend beyond either point; though it is not inconceivable it could make a veer out to provide a station in Malvern.
I wonder if/when CDPQ Infra will look somewhere other then Montreal for their next project. (Since the REM de l'Est has been stupidly canceled.)
I am told CDPQ is considering exiting this type of build entirely. REM de l'est is only a part of the issue. Nothing has been decided yet, and CDPQ will doubtless do an extensive post-mortem once the currently under construction services are in operation.
But I can say there is much unhappiness from every player.
Things that seem too good to be true, often are.........
Come to Toronto says I, build a line from the Scarborough Convention Centre to the Ontario Science Centre, to Summerhill Station, Dupont Station, then head all the way to Mississauga City Centre.
There will be a line in that corridor, one day, it will be a GO Line.
The Mid-town corridor is owned by CP Rail the complications of building elevated over their tracks are almost certainly too difficult to conquer.
The clearance heights would almost certainly have to allow for double-stack freight..............not happening.
Besides, there is room along the majority of the corridor for a dedicated set of tracks for GO, though some expropriation, retaining walls and widened bridges will be required; and that would be much cheaper than unnecessary elevation.
That said, this investment will not come soon, its not even on the medium term horizon. (15 years).
Beyond current 'Go Expansion'; the priorities are 2Way-All Day on the Milton portion of the corridor with a near-term goal of 30M frequencies, along with the extension to Bomanville and towards Niagara, then adding Cambridge into the network in one fashion or another is on the list after that.
GO Midtown will follow; though its one of two cross-town routes being looked at and only one will go forward in the next 20 years or so.