My guess that the secondee situation is likely to go the other way .........
Now that BA has managed to set up a separate low cost operation.
BA could pull back its F/O,s that currently have command slots at GSS.
GSS does not want them as it screws up promotion for GSS F/O,s and causes their copilots to leave GSS because BA pilots take half the command slots, the extra training must cost GSS .
The original deal was brought about by a BALPA demand.
BA would want a cheaper charter deal no doubt from GSS after if they did the dirty on that one no doubt.
It seems to me, to be a possible next test by BA to see if BALPA would again back down in face of the new legal barrage that would inevitably result
GSS is not even a BA subsidiary so the BAPLA legal position is weak.