You cannot compare BALPA's open skies fiasco with BASSA's ongoing concern. BA was within the law of opening up a base in NY which had no bearing to BA crew based in the UK.
Imposing changes in your T+C's without agreement is a completely different matter. As long as BASSA have conducted themselves in a correct manner I see no probs.
One of the reasons why BASSA reps have not been posteing on forums, as this would play into BA's hand.