Right. JPM's suit is filed in bk court and names WMI as the defendant. Remember, the original WMI suit from last week was filed against the FDIC. So, technically, it's not a countersuit, but a preemptive attempt by JPM to protect itself against any repercussions from the WMI vs FDIc suit.
As Islandcat stated, JPM has thrown the FDIC under the bus by claiming it stole WaMu fair and square, and any problems with that are on FDIC's shoulders.