People keep posing the question "why is WW so determined not to conceed OS pilots the right to join the mainline seniority list"?
I feel it is quite simple, BA pilots are highly organised with a rostering system "Bidline" which takes roster control away from the management.
For years management (LCG springs to mind) have been trying to disemble Bidline, claiming its costly, in fact it is not, but "They" feel it takes away their right to manage. Macho management hate this.