Aren't they trying to stitch up the BHX and MAN crews with a BACE contract? If so, this is probably where the rumour started. If it isn't going to happen and the JFK is to continue ex MAN, then the alternative would be that cabin crew would have to come from mainline at LHR.
Why did they have to screw the regions up?
Damned if you do, damned if you don't.