What is absolutely certain is that nothing is guaranteed. No matter what cadet scheme you are on anywhere in the world, there can never be an actual guarantee of employment.
LOT have run a cadet programme with BAA before. Perhaps it would be prudent to ask BAA about the previous cadet programme and try to contact some students from it to see their progress. Visiting the school, touring the facilities and speaking to current students out of the earshot of sales would also be sensible.
I have never been to BAA and don't know anyone who has. There are threads on this forum though regarding the school and a search of them may be enlightening.