Hunterboy,
Despite Fume Events interpretation of things it is, sadly, not so clear cut.
Firstly BA will claim that it has attempted to negotiate with BASSA, above and beyond that which it was required and it also extended deadlines and involved ACAS, all to no avail.
BA will claim that the reason for strike, whatever it may be from the rather broad brush that BASSA have posted on their ballot, will damage the business and is illegal. Especially as the strike 'cause' has already been initially tested in court and BASSA lost. So expect BA to call the strike illegal and that BASSA should wait until the full court case in 2010.
BA will also state SOSR as a reason for preventing damaging industrial action and the reason for implementing changes in the face of an incalcitrant union. Look at the current environment where Air Berlin is losing money, LH cannot support an almost bankrupt BMI, AF/KLM are laying off people left right and centre and Virgin are teetering on the brink and still BASSA wants to keep 1970's T's & C's. Think public opinion is behind you? The expenses that are tacked on to a long haul flight are almost at MP levels.
So, even if the 'strike' were to be legally balloted the danger to anyone who takes action based upon flaky advice by BASSA runs the risk of subsequent dismissal. That dismissal may indeed be illegal BUT BA can pull it for years through the tribunals and THEY DO NOT NEED TO GIVE YOU YOUR JOB BACK!
So, if BASSA want to play hard ball and bend the rules don't expect BA not to.
Good luck.