It’s not the first time that Wall Street investors are asking where the interests of billionaire bond king Bill Gross and the Obama administration diverge. Gross, who has been consulted on Treasury Department decisions that have benefited Pacific Investment Management Co., his bond company, has joined with the Federal Reserve Bank of New York to open what could be a major can of worms. Pimco and the New York Fed are preparing to sue Bank of America for selling $47 billion in bonds based on subprime home mortgages that the bank allegedly should have known would default. The lawsuit could boost the value of Pimco’s investments, but it might also encourage a wave of similar lawsuits against banks that issued hundreds of billions of dollars of home loans to people with shaky finances, according to Robert Litan, a finance expert and former Justice Department official in the Clinton administration.