Building on that idea, one of the big picture problems with transit planning in the suburban GTA is the land use planning has been based on automobile corridors, not the existing transit corridors. Both the Scarborough Town Centre and the Mississauga City Centre are located to be fully accessible by car, but that makes them difficult to access by existing major transit lines. The SRT is effectively a shuttle bus that takes people from where the city centre should be, if it were transit friendly, to where they located it to make it automobile-friendly. If major high density nodes were located around or adjacent to existing GO stations - the GO system could effectively become the "subway"-level transit for the GTA and a network of lower-cost LRTs and BRTs could service the areas in between.
Notwithstanding the cost differential and level of service, if you want to get from Kennedy station to Union station by far the quickest way is to jump on the GO Train (26 minutes for GO vs. 41 minutes by subway). So increase the level of service and reduce the fare for GO and there is no need to build a new multi-billion dollar subway line. Then leave the STC as a suburban mall and make areas around the five or six existing GO stations in Scarborough the new high-density development nodes. The same would apply for all suburban areas in the GTA. Don't bring the transit to the development, bring the development to the transit.