As a BA pilot I would have no objections to your seniority list being merged with ours (If you're referring to GB Airways). The fate of CFE and Dan Air have riddled our seniority list with anomolies, Grandfather rights and most of all it has made too many of my colleagues demotivated and cynical.
We have too much to lose if GB/Bmed are played against us as 'alternatives' so to share resources would make both business sense but also provide a little more protection for our futures.