Is BA trying to do the same to pre empt a low cost long haul carrier from doing this out of Europe??
Perhaps. It would make a certain element of business sense. Both sides acknowledge that this would be unworkable using Bidline Rules as costs could become prohibitive. Similar to the LGW shorthaul operation. In fact, BALPA have effectively conceded to any T&Cs that BA want in exchange for OS pilots to be on the seniority list. This would negate any cost disadvantage immediately.
The question you need to ask though is this one.
If BALPA is prepared to concede to any terms and conditions desired by BA to allow Open Skies to operate at the initial cost base planned by BA, why will BA not permit OS pilots to join the mainline seniority list?
No-one in BA, not even WW, is prepared to give an answer.