I don't think there is much chance BA have 'meddled' this time. The regions can provide relief for Heathrow and the JV means they get the same amounts whether a pax travels via LHR on BA or direct to ORD on AA.
I think this is purely down to more P2P being available from MAN and thus the legacy hubs were bound to feel the pinch.
As for UA to EWR, some interesting seat plans showing up in one GDS starting 23rd May, so looks like they could be ones to benefit from AA pulling JFK.....