A False Claims Act case may be brought if any portion of the money to pay the claim comes from the US Treasury.  Here, the claim was that Wisconsin Bell cheated the E-Rate subsidization fund of money by charging subsidized schools at higher rates than legally allowed thus generating inflated claims against the subsidy fund.  Though most of the subsidy fund came from other telecommunications carriers, the US Treasury transferred $100 million to the fund representing moneys recovered from defendants in government suits for fraud on the E-Rate program and other similar prosecutions.  That infusion of federal money was sufficient to make the FCA applicable.