Forgive my ignorance, I have never worked for either BA or GB, but wouldn't placing the GB pilots on the BA seniority list only really benefit BA pilots?
In the event of an expansion, being on the BA list might eventually enable a GB pilot to bid for 744's at LHR. But in view of the probable down size in mainline, the most likely scenario would result in the GB pilots being used as cannon fodder as most of them would be propping up the bottom of the combined list.
When BA is reduced in size, they would be the first to go with their commands going to "redundant" long haul pilots.
