AFAIK is available for any Amex Plat cardholder. I knew at least 5 Am Plat holders who went there a lot of times. GRU is a small airport, with 3 terminals connected by a corredor. The "Salao Centurion" is in Terminal 1 (at the mezzanino, so take the elevator or stairs) and BEFORE inmigration area. It is out of the boarding area.