Here is another informed view - without any union claptrap.
As far as I understand it, BA and BACX are seperate legal entities or companies. Hence, seperate AOCs, pension schemes, T and Cs and the like. BA could become bankrupt without bringing BACX down, or vice versa!
Surely then, those who wish to join BA may apply for positions that are available, irrespective of their present employer, just like dear old ETOPS did when Manx was an airline in its own right.
The fact that both airlines, BA and BACX, ultimately have the same ownership is of no legal significance here. I think that it follows that there would be something called a tort in effect if Big BA excluded BACX pilots from appling for available jobs in BA if and when they start recruiting.
It's a free world mateys and you do not need to abide by any artificial restrictions placed on your employment by either your employer, potential employer or union.
Of course, there is a real world out there. Being shafted in your aspirations by any cosy arrangement made between BACX pilot management, a BA secondee don't forget, BA and/or the union would be a real pi55er wouldn't it?
Any legal mind out there care to comment or, indeed, anyone care to give it a run?