Time for something on a broader scope. As I see it, the only way in which we are going to see true electrified 250km/h+ high speed rail west of Toronto is if it is done piecemeal. The Kitchener line is already on the Metrolinx priority list for electrification. Given the straightness of much of the existing Guelph Subdivision, and the fact that it could be up for purchase in the next few years when GEXR's lease is up for review in 2017, I could see a scenario in which Metrolinx takes over that lease. Doing so would make rail upgrades, electrification, and conversion to EMUs on the north mainline far easier given that the line would be under Metrolinx control. I'd like you to consider the following ultimate setup:
From London to Pearson
From Brampton to Union
The black line is the fully electrified mainline from London to Toronto. Red lines are potential high speed bypass routes and would be built on an as-needed basis as the line gains ridership and grade-separation through smaller towns becomes prohibitive. The teal line is the Pearson rail spur.
The following services would be run on the corridor:
High Speed Rail (Red Stops): Running up to a maximum of 325 km/h based on track geometry. This could be operated by a consortium of private companies under the Government of Ontario, or operated by VIA depending on appetite.
Intercity Rail (Yellow/Red Stops): Former VIA Rail operated by GO transit. By this time, VIA will likely want to divest its intercity service on the North Mainline in favour of running more direct service on the Lakeshore-Brantford corridor
GO Express Regional (Green/Yellow/Red Squares): This service would connect Kitchener to Toronto with a run time of about 1h 15m hitting major stops and transfer nodes along the line primarily during rush hour both inbound and outbound, but could be extended to operate all-day.
GO Local (All stops except Teal): A local service which would be timed to make transfers with the GO express service both inbound and outbound.
Union-Pearson Express (Union-Bloor-Pearson Terminal 1): This would be an actual express service to connect the Airport with Downtown Toronto)
Union-Pearson Local (All Stops): This line would serve the function as a western leg of the DRL (terminated at Dundas West-Bloor) providing a more local, frequent rapid transit-type service with shorter high-floor EMUs compatible with the existing UP Express stations
In terms of timeline, I'd optimistically hope for full buildout by 2045. The local service on the UP right-of-way I can see being looked into following the Pan-Am games. Electrification to Kitchener would probably take until at least 2025 and past Kitchener until 2035. High speed sections would need to wait until a tunnel is built beneath the existing rail corridor for Lakeshore service and for the buildout of the Toronto-Ottawa-Montreal high speed corridor. The Stratford and Acton bypass tracks would be the last piece and would be built at an even later date.