Sorry to resurrect this oldish thread but I have a related question and it seemed foolish starting a new one.

Does anyone know if the whole upgrade with cash (either MMB or airport on the day) applies only to BA metal or not? I'm looking a upgrading a flight to MEL that is operated by Qantas but booked through BA (at least it will be eventually... Before pulling the trigger I am researching whether I can upgrade this to WT+ at a later point, as my employer will only pay for Economy).

Thanks