First, this is the driver mode share for all trips (not just commutes) by location of residence. This is based off the 2011 Transportation Tomorrow Survey data, which sorts trip in the GTHA into the transportation modes of driver, passenger, walk/bike, GO transit and local transit (as in provided by a local agency, it includes subways).
Next, a similar map, but this time showing driver mode share by destination for the whole GTA.
side note: some of the suburban communities had very small wards, in which case they were combined with adjacent wards. I've been aiming for a population of 30,000-60,000 per ward. Oshawa does not have any wards, so I just gave the data for the whole municipality. If there's interest, I might update the post so that all maps are GTA wide, but for now I'll mostly focus on Toronto proper.
Income should have less of an effect here, since we're looking at mode share by destination. Again, driver mode share is lowest for downtown, followed by the west end. There are wards in more suburban areas with relatively low driver mode shares, many of these have important post-secondary education campuses. School trips are 7% of the total in the GTA, here's how the wards with important campuses compare
Toronto Ward 1 (Humber College North Campus)
Driver mode: 54%
Percent of trips that are to school: 20%
Toronto Ward 8 (York University)
Driver mode: 47%
Percent of trips that are to school: 31%
As for why Scarborough has lower driver mode share than North York and especially Scarborough, I'm not sure, but there is one possible reasons I can think of. First, although they all have similar development patterns, Scarborough is a bit more isolated from wealthy outer suburban areas so these make up a smaller part of the local labour market while a lot of the commuters come from within Scarborough, compared to North York and especially compared to Etobicoke.
Using 2006 TTS data (905 is the area code of the outer suburbs)
Location of residence of employees in Scarborough
Other Toronto: 22%
Location of residence of employees in Etobicoke
Other Toronto: 28%
Location of residence of employees in North York
North York: 28%
Other Toronto: 36%
Perhaps the pattern is also similar for non-work trips.
Next is a little map where the value mapped = [driver mode share for trips made by ward residents] - [driver mode share for trips made to the ward]
A negative value suggests it would be somewhat hypocritical for ward residents to complain about outsiders creating traffic in their ward whereas they would be more justified to complain when the value is positive.
Many of the most positive values are in wards with a lot of employment that's accessible to outer suburbanites by highway, but where local residents are more working class and more likely to take transit. So outside downtown, residents would have some justification for complaining about traffic caused by 905ers.
Here is a map of transit mode share of trips by location of residence.
Transit mode is not quite the inverse of driver mode - downtown has a high walk/bike mode share, which not only cuts into driving but also cuts into transit use a little. As a result, the west end has a bit higher transit mode share. This is why a significant benefit of having a growing downtown and downtown adjacent population is that not only do residents drive less and require less auto-infrastructure per capita, but they don't even require that much transit infrastructure per capita, especially since not only is transit mode similar to the rest of Old Toronto, but transit trips are shorter. Meanwhile the cost of pedestrian and bike infrastructure is very small, and doesn't even increase much with use - the suburbs often have sidewalks too, despite having much fewer pedestrians.
Transit mode by location of trip destination.
Finally I've combined transit mode share for trips made by residents of each ward and trips made to the wards.