Well, you learn something new every day - although I'm a bit surprised that the C40 (737-700C) has the legs for it, with a range of 3000 nm I'd have thought US mainland to UK would be a bit of a stretch. (Maybe the great circle chops more off than I thought <g>).
I rather took Elmo to be suggesting that the P8 engine noise would be disguised by the commercial 737 traffic, and whilst I've finally managed to convince myself that a twin engined 767 is okay for a trip across the pond it DOES have a teensy bit more range...I still don't think the P8 will find a great deal of 737 traffic masking it.