I recently tried to take a guest into the RCC in Atlanta and was told the same thing - Aeroplan members = no guest. I talked him into it and he acted like he was doing me a huge favour (the guest was a MP gold member by the way). Star Alliance clearly states a gold card holder is entitled to one guest. Perhaps they are superimposing rules for Maple Leaf Lounge paid members with Aeroplan E / SE gold cardholders?