At GRU LAN uses the AA Admirals Club Lounge.
Unless LAN have some special arrangement there Oneworld status will count for nought on a flight not operated by a Oneworld carrier.
My experience at EZE as a AA EXP/OW Emerald flying Business class on a LAN-coded/TAM-operated/AA-issued ticket transiting from a QF 1st class flight was that neither LAN or AA wanted to have anything to do with me. The LAN transit desk had no interest in my questions referring me to the long line at the TAM desk.
Hopefully this will all soon change ? for the better assuming TAM integrates into Oneworld