The Province's cancellation of the Missing Link project was justified based on the fact that CN would permit all-day GO service to Kitchener on an upgraded CN Halton sub, presumably 1 or 2 GO trains per hour.
But the Missing Link wasn't just a way to bring an hourly service to Kitchener, it would have been a total game-changer for passenger rail west of Toronto, creating a passenger-rail-controlled corridor from Toronto to London. HFR West would become totally practical, as well as frequent local service which actually makes it from Toronto to downtown Brampton rather than turning back one stop short at Bramalea. As
@crs1026 mentioned, CN's traffic is pretty light between London and Kitchener, so they probably wouldn't mind selling that segment to ML or VIA (while retaining trackage rights). The main reason that hasn't happened yet is that without the bypass in place, the passenger agencies can't count on running enough trains to justify their investment in the line.
Here's how that dedicated passenger line could fit into our mainline rail network:
Green = Metrolinx/GO
Red = CP
Blue = CN
View attachment 305492
In this scenario I showed ML owning the line all the way to London, but VIA could equally own the segment west of Kitchener if that works out better logistically.