On a recent trip, BA in Toronto checked my bags through YYZ-LHR-DUB and then on to an EI ticketed BA codeshare DUB-EDI....There was a bit of "computer says no" to overcome at the desk; it was of course before the recent OW separate PNR rules including barring BA to BA; and all that said, one of the bags missed the DUB connection and turned up a day late...

But if you ask nicely, it can be done....or at least it could be.....