Entaxei, can I refer you to a recent post.
We all agree that BA can withdraw staff travel at their discretion but it's the reason they have withdrawn it that counts.
If the reason for withdrawal is to punish a legal strike, they may be on dodgy legal ground. The point has also been made that we are talking about the principle of punishment for striking, the fact that the means of punishment is staff travel in this instance is irrelevant. Your post did not debate on that point at all.
There are wider issues involved than BA's provision (or not) of staff travel. BA does have the power to withdraw staff travel, but their doing so could set a precedent throughout employment law as it relates to strikes. This is what any court case is likely to cover. As Call100 says, it's not as simple as ' BA can withdraw staff travel whenever they want'.