BA pilots are also just like any other group of employees within the company and are just as liable to be replaced or outsourced
Which is why no profitable major airline anywhere in the world has succesfully outsourced its entire flying operation. Get real folks. BA is an airline. It flies aircraft from A to B. That is it's business. Nobody outsources their core functions or they cease to be.
I never cease to be amazed by the people who decry 'management' and their Harvard MBAs then tell us that if they were running the airline they would outsource everything, which is itself a Harvard strategy of quite some vintage!