The City Council will not pay for Sheppard subway, at least not in the next 15 years or so. The majority of councillors will feel that the BD subway extension is a good enough deal for Scarborough.
Thus, if Brown's Tories want to put the Sheppard subway on the table to win those 4 ridings along its route, they will have to fund it entirely with the provincial money. As I understand, the Federal infrastructure money will not be available for projects that have no municipal contribution.
I doubt that Tories will do that, given their inclination to cut both taxes and deficits, and the competing demand for transit funding from smaller cities where their electoral prospects are better, anyway. They might lose more support outside 416 if they give too much money to Toronto at the expense of other municipalities, and that loss might offset the benefit of getting those 4 Scarborough ridings.
My forecast: no Sheppard subway anytime soon, no matter who wins the next provincial election. On the other hand, Yonge North extension might get a boost if Tories win, and it might overtake DRL despite the fact that DRL should be first from the rational technical standpoint.