My experience of outstations is that upgrade decisions are usually validated by the station manager in person (or one of his/her assistants if he/she is not around). I think in most cases, these decisions are based on a mixture of booking class, status, PNR messages, and number of passengers on a booking. I think that any attempt to suggest that any of these aspects has 'nothing to do' with the decision is definitely a caricature but the order in which these elements are weighted can certainly vary. May I ask about the circumstances in which the discussion took place? Maybe the GA thought you were trying to get an upgrade and just wanted to 'get rid of you' by saying that your card didn't matter because of a low booking class? My interaction with airport staff friends in various airports (sadly none of which I tend to use a lot!
) is that they all keep repeating me that they hate it/feel embarrassed or annoyed when people ask them about/for upgrades so it wouldn't surprise me if many tried to cut these discussions short.