TTB
The upshot of the whole exercise is that the company has the ability to decide which CC it wishes to retain and which it wishes to remove.
For the customer the whole thing is totally transparent as the two contracts run side by side.
Personally I hope it never comes to it and that BASSA are bankrupt by BA in the upcoming court case. I will be highly surprised if Unite don't seek a settlement before the court case as the punitive damages to BA could run potentially into hundreds of millions. Something I am fairly sure those Unite members struggling in other industries, where they don't get paid well over market rate, will be very, very annoyed to pay out for.
Good luck for your trip. I will be there and working, even in the cabin if required trying not to spill a cup of tea, it's a tricky job!