Basically no. That paragraph is there for a number of reasons but staff travel isn't one of them.
There has already been a similar court case although in reverse. The employer offered free flights to all those who continued to work and refused to take part in strike action.
The strike duly finished, the union waited until the first person took up this offer and then successfully went to court on the basis of discrimination to get strikers a free flight as well.
They won apparently because the strikers had done nothing wrong and so the offer of a free flight for some employees and not others was discrimination.
I have no axe to grind in this dispute mainly because I have no idea whats really going on between BASSA and BA. However the staff travel issue is below the belt, uncalled for and my money is on it biting BA back very hard.
Again you should be careful what you wish for. This tactic has serious implications for everyone if not very quickly beaten back down.