But what have the people who have lost staff travel got to loose?
The flippant answer is whatever it is they'll have lost it well before any ECoHR case hears their claim.
The serious answer is that this isn't just about the BA staff affected. The cost of such a case would add another million or so to Unite's legal bills in support of BA cabin crew. Why should the 2 million members who aren't affected be paying for all this? If BASSA wants a degree of autonomy within Unite, then shouldn't BASSA's costs be similarly ringfenced from the rest of the Union? From the outside looking in, BASSA appears to wield a lot of power within the Union, but with very limited responsibility. Unite and BA's interests with respect to BASSA look remarkably well aligned to me!
Also, Unite is now one of several Unions looking at very significant job losses in the public sector. Personally I think the 600k estimate of such losses is probably excessive, at least within the next 4-5 years. 300-400k looks very possible though. I don't know what proportion of affected workers will be Unite members, but even if it's only 10%, that suggests 30,000-40,000 members at risk, which puts the 2,000-3,000 BA staff at risk of nothing more than losing staff travel into some kind of perspective, even if such a loss results in some of them having to leave BA's employ.
Unite needs to get a grip on BASSA even more than BA does. I rather suspect that, given the choice, most Unite members will want to reserve £1 million to fight job losses/pension losses etc in the public sector, rather than campaiging to establish the fundamental human right to cheap fares for airline staff. What influence do the 2 million plus non-BASSA members of Unite have in determining how the Union's overall income is allocated and spent? How are you justifying the ongoing transfer of value from your members to BASSA via strike pay subsidies and legal fees etc? And are your members supportive of this transfer of wealth.