Overall, this is a good idea, but there are a few foundational problems with this plan.
For one, anyone who rides the Georgetown GO Train knows that Mount Pleasant station is currently under-serviced. There are currently only
4 trains that stop at Mount Pleasant.
Look for yourself, the trains are highlighted in green. Despite being called the 'Georgetown Line', the Georgetown GO Train more often ends its service at Bramalea Station, two stations short of Mount Pleasant, and the train doesn't run on weekends or off-peak hours. Metrolinx wants to increase the Georgetown train to as much as 300 trips per day, but who knows when that project will be completed, if ever. I have my doubts.
For another thing, why are we investing in TOD development in the middle of a greenfield, at the periphery of the GTA? For a TOD mixed-use site to be economically sustainable, it needs to not only provide amenities to the people who live within the development, it also needs to attract people from outside the development as well. Why would I, a Torontonian, ever want to get on the Train to go out to Mount Pleasant? Even if I lived near Bramalea Station, would I get on the train to go to Mount Pleasant? Even if GO increases service, the service will still be oriented toward Toronto, and most of the trains will operate during rush hours... not conducive to bringing in consumers to the neighborhood.
Finally, nobody that lives in this development is going to live car-free. See points one and two. You're basically out in the country, and having a car is just part of the culture there. What's more, you can't really live car free there. Where's the school? Where is your municipal services centre? I'll bet anything the mixed-use retail that emerges will be limited to a couple bourgie boutiques, a Sobey, a Gap or similar discount clothes retailer, a Starbucks, and probably a Inuit Art Gallery or something. Where's the home-owner going to go for furniture, lumber, peat moss...
I'm very sceptical.