Yes, CO does do BRS-EWR with a daily 172-seat 757 (started in May this year).
It has had a slowish start with the real problem apparently getting Americans to use it.
Things seem to be picking up with nearly 9,000 using the service in August (if that month had been poor eyebrows would be raised) giving a load factor in the low 80%, and signs for September appear good as well.
BRS has a throughput of 5 million pax annually compared to BOH's approaching 3/4 million, so on the face of things it would seem that BOH would struggle to successfully operate a daily 757.
I'm not sure of BOH's realistic catchment area. BRS is said to have 7 million in its own but there are other airports within and on the fringe of this as well.
Also bear in mind that Greater Bristol is the major economic force for the whole of the government's southwest region, which includes Bournemouth and Poole, so that is another reason to suspect that BOH might struggle even to emulate BRS's relatively modest, but improving, performance on the 'New York' route.
Unless of course there are specific circumstances in Bournemouth and district for
thinking a New York service would work.
Good luck anyway, the more routes the better, so long as they are sustainable.