Historically, the federal government tends to directly subsidize transit capital expenditure, not operating expenditure. However, with operating budgets collapsing nationwide, Chris Dodd and seven other Senators have proposed a $2 billion fund to help transit agencies through their current revenue trough. Local reaction here (summary: Yipee!).
It’s important to understand that this is an “authorization”, not an “appropriation”, so even if this measure passes lawmakers would have to add it to an appropriations bill sometime in the next 16 months. This comment covers how the money would be distributed; since I’m entirely ignorant of the relevant statutes I’ll just say that strictly according to King County’s population, Metro would be in line for $12m. That’s perhaps a quarter of the deficit in 2012, so it’s nice, but hardly solves the problem even in the short term.