The P-8As are so much more versatile than the old P-3s are. They can drop multiple types of Sonobuoys, torpedos, Harpoon missiles, overwatch and battle management capabilities, and now apparently Elint capabilities as well.
I think you are on to something here. Been noticing that they have been doing orbits inland and was trying to figure out why beyond accumulating training hours. This may be the reason. Bet the tech in that pod blows away any of the Stingrays that law enforcement have. Still I do think that they have been scanning for threats to the East coast as well, their positioning over major harbors seems too strategic to be a coincidence.