As I also stated in my original post when I originally heard about this the story I heard was that BA had some alternative catering arranged, however BA's unionised staff were refusing to deal with aircraft that were catered by a Company other than Gate Gourmet, effectively supporting the action of the catering staff.
This could be classed as highly illegal secondary action. The GG staff were on unofficial strike. BA staff have no right to refuse to deal with other caterers. BA would be perfectly within their rights to discipline or sack anyone who refused to work/deal with alternative caterers.
I would be surprised if Skippy or WW would not look to use this as a (legitimate) excuse to get rid of a few troublemakers without having to make any pay-off.