BALPA fully recognise the need for appropriate costs and scheduling agreements in PL, what they want is for all PL pilots to be on the Master BA Seniority list ie to enable people to move between the various bases and fleets. It may be B757 today, but tomorrow if it is a success it could easily be a B777 fleet. All BA pilots want is for BA flying to be done by BA pilots.
That seems like it shouldn't be too hard to accomplish by both sides, are BA really that resistant to that? I guess the issue is they want to pay PL pilots a lot less than mainline pilots and is this something that couldn't be done with PL pilots on the main list? Just trying to understand the pilots point of view in this as well.
It doesn't affect me either way whether BA pilots fly it or not but then if it is the start of a slippery slope towards moving other stuff away from mainline, eg BA functions currently undertaken at LHR but could in theory move elsewhere then yes it does. So if that is an issue BALPA are also worried about as well then it has my, and lots of others i would imagine, support.
Lets hope that in a few years time it is indeed 777's flying those routes from Europe!!