Chugalug2,
All seems pretty straightforward to me.....
1) The RAF has a near-term shortage of pilots They have a plan to address it in the medium term through recruitment and training.
2) BA has a relationship with the RAF through the managed path scheme. And has done for decades.
3) BA has a temporary surplus of pilots and is willing to loan them out to the RAF. A win-win.
BALPA cannot order airline HR departments to set up sabbaticals for pilots. It can encourage companies to liaise with the RAF and no more. This is not a BALPA issue.
As has been said, any UK airline pilot can apply to the RAF and see how far they get through the selection process. Any ex mil pilot can apply for the rejoinders scheme. That’s not a closed shop.
Finally, are you aware of any other companies that have approached the RAF with a request to place pilots under sabbatical arrangements?