That was, as you said, for unlawful action. The Gate Gourmet dispute was not a BA dispute, (the catering had been subcontracted, and BA's own catering staff taken on, on the whole, by Gate Gourmet, it may have been, not sure, that BA sold off it's catering to GG as a lump, staff included) but secondary strikes at BA were encouraged in support, and that was clearly unlawful. The CC strike, however misguided the reasons, was lawful.
Still, if they lost staff travel as a punishment, it does at least mean it has happened as a result of a disciplinary situation, which was a question I asked earlier. Striking CC are not going to be on disciplinaries however, not just for striking, so it's unclear just how relevant it is to this.
I shall certainly watch any court case with interest.