I also have the feeling that people who live in the core, come out in higher numbers but that's just a guess. Anybody got stats on that?
From a quick look at the wikipedia page for the last election:
http://en.wikipedia.org/wiki/Toronto_municipal_election,_2006
It appears that suburban and urban have some difference, but not a major difference in terms of voter turnout. Etobicoke and North York look like one of the worst areas for voter turnout - about 10,000 to 12,000 votes for some wards. Scarborough appears to be better. Some downtown wards like one of the Parkdale wards, and St Pauls have "big" turnouts of close to 17,000 to 18,000 people. (BTW, didn't know that John Sewell ran for St Paul's or that Case Ootes won by only 20 votes. The things you learn from wikipedia!)
I'll leave the exact calculations to someone else, but a basic guesstimate for the potential voter turnout for the suburbs is prob 250,000 for the suburbs and about 300,000 for the "city". Not skewed enough to the city to make a RF victory impossible, but he does have a bit of an uphill battle. David Miller got 333,000 votes last time and nearly 60% of the vote.
It should be pointed out that RF is not even a runaway success in his home turf. He got 66% of the vote in the last election - respectable, but not particularly mindblowing for an incumbent. Adam Giambrone got about the same percentage, and neither of them are as popular as Joe Pantalone is in his ward (77%). And that despised public figure, Sandra Bussin, received 2,000 more votes than Rob Ford in the last election.