not since the '30s has this happened. according to the fantastic book "stigum's money market," reserve banks are authorized, "in unusual and exigent circumstances" and after consultations with the Board of Governors, to extend credit to an individual, partnership, or corporation that is not a depository institution if, in the judgment of the Federal Reserve Bank, credit is not available from other sources and failure to obtain such credit would adversely affect the economy.
The interest rate charged on such credit would be above the highest rate in effect for advances to depository institutions. Such loans were used in the 1930s to grant about 125 loans totaling a mere $1 million, but it has not been used since."
other sorts of federal subsidies or assistance, the fed believes, should be granted only by decisions of congress and the administration, not by an independent central bank.