I am not going to go into final salary pensions... for instance a group of staff (the majority) who have 7 increments and often in my department work for 49 years 42 on top increment and then retire versus one department that has 24 increments for an fo and a further 24 for a captain so effectively one could hang on as a career fo for 30 years ending up on pay point 24 fo and then five years before you are due to retire and enter a type freeze. Take a command course and jump to pay point 24 captain- a close to 40000 pound pay rise and profit from that when you retire five years later having only made five years contributions at that top rate.
Firstly FO pay is capped at paypoint 18 so there is no such thing as a pay point 24 FO. Secondly If said FO chooses to take that 25% pay reduction by not becoming a captain a more junior guy will take his command instead so someone will be paying command contibutions longer than they would otherwise so there is no net loss to the fund. Additionally BA would be apying a lower paypoint command salary too so they would gain.
Also there is presumably a chance to be promoted to other grades in your dept (I appreciate there is no guaranteed promotion) but if you did get a promotion say 5 years before retirement would you not expect to gain in retirement from that?
As for secret deals, well all the unions (except those that were too busy) were at the meeting so i dont see what the big secret was.