Litebulbs
BA don't have to do anything. If the latest offer is rejected, they can leave it at that. The onus is on Unite to make a move. If the union cannot find a reason for calling a strike ballot that is on a wholly new topic, unrelated in any way to the previous action, then the can try that. The snag is that they will need to not only get a majority in favour, but also be able to ensure that sufficient numbers walk out such that BA's operation is severely hampered. That's where the problem now lies. Unite have lost a chunk of members. There are a raft of new joiners in Mixed fleet who may be less inclined to walk out and there are all the volunteers. So the strike weapon has been effectively neutralised. BASSA's teeth have been drawn. I reckon that over time a growing number will become disillusioned with the branch and leave. This may get to the point where the branch is derecognised. Those who went on strike will eventually start feeling the pinch as they will not be getting the pay rises that the non-union folk have signed up for. Neither will they be getting the top up payments. Those who relied on staff travel for commuting purposes will find it increasingly expensive to get into work. All told I reckon there will be an increase in staff turnover as these folk find it less attractive to work for the airline. Their replacements will join Mixed Fleet. I can also see that BA might make the offer - minus the staff travel seniority return - at some point in the future to those who are no longer in the union. What BASSA are doing is accelerating the time scales for the introduction of Mixed fleet by sticthing up their members. The fact that it will bring about the branch's own demise seems to have escaped them.
I doubt that BA will go for dismissals for SOSR, simply because that might invite a further dispute.