What I find puzzling about this is that the Hong Kong crew have never been represented by BASSA/Amicus in BA. They had/have their own union in HKG.
BASSA did sign up a number of ICC's some years ago but BA refused to acknowledge that they were represented by BASSA.
The South American based crew did belong to the TGWU going back decades to BCAL.
The Narita based crew are represented by their Japanese union and they get some pretty good deals. I guess they would not be happy if this case is won and BA put them on UK T&C's.