How? Unless we repossess everyone's property, flatten the suburbs and coerce everyone to move into high density housing and then build transit hubs up to each housing unit.... this ship has sailed. Look below, if you live on one of these cul de sacs and you work downtown Toronto, there's no way local transit (especially if we exclude buses) can get you to the Go Train station. And I exclude buses because I hate them, noisy, rattling, crowded, smelly things used only by the desperate, becrippled, schoolaged and poor. Even if we included buses, there's no way they could serve suburban daily GoTrain commuters in neighborhoods like those below.
Here's Ajax...
Here's Milton...