That there were no BA groundstaff waiting at AGP isn't surprising seeing the flight wasn't expected. Likewise the apparent delay in getting the buses.
In terms of getting from AGP to GIB there are 2 options - wait for the fog to clear and fly there, or get the pax onto buses. MON went for the former strategy, BA for the latter. MON guessed right, BA looked a bit stupid. But things could easily have ended up the other way around had your bus reached GIB as the MON pax were still in AGP.
Hard to see any real cause for complaint - even as far as food goes supplying it would probably have delayed your arrival in GIB even more.