S&P has a new report out with some calculations surrounding the MTA’s forthcoming 2010-2014 capital plan, a draft of which the authority released last week.

The plan is $28 billion, 20 percent bigger than the program for 2005 through 2009.

Of the $28 billion, $9.9 billion — 35 percent — is hole, with no source of funding.

But it gets worse.

As S&P’s Laura A. Macdonald notes, the plan assumes $8.2 billion in federal funding, which would be a 25 percent increase in the historical federal formula.

The idea is that the feds will increase funding after finally “recognizing the backlog in investments in transit across the nation.”

But with

• a federal deficit of $1.75 trillion, or more than 12 percent of GDP, for this year,
• not much improvement expected for next year’s federal deficit,
• No real assurance that the federal government will be able to continue to borrow at cheap rates to fund spending hikes,
• Washington already scrambling to figure out how it will pay for health care,
• and not much having changed with regards to support for mass transit in the rest of the country, and thus for most Washington lawmakers’ interest in the matter,

… it’s not totally apparent that President and Obama and Capitol Hill will take the heroic, enlightened stand on mass transit that the MTA expects.

The plan also “assumes $100 million a year in city funds …, up from the current $80 million a year. And it assumes that another $600 million will come from MTA asset sales, pay-as-you-go capital, or other internal sources.”

These tenuous assumptions are yet more evidence that the MTA’s generous senior-citizen discount for Atlantic Yards developer Bruce Ratner — allowing him to pay just $20 million upfront for valuable Brooklyn property rather than $100 million, and giving him lots of other stuff, too — was a bad deal.