Regarding the numbers of a/c being queried..A further clue may be last year when the aircraft intended for repatriation all positioned or had in the system ready for use the airline flying as prefix but then the pre-existing MON digits to the particular allocated service...
It makes sense to all involved parties to fly ALL the pax home on the same flight they were due to with MON originally & then re-distribute costings later..
Evidently MON is solvent @ the present time with £10`s of millions in the bank too so call could be made on those funds to help their customers unprotected by ATOL.