I have an older Mac, and went back to pre-Rev A for my own reasons. But I remember that with Rev A some of the files are stored in a different place (same volume as the OS, user folder IIRC) than where the game itself is installed, and the folder names were, IIRC, confusingly similar.
Hopefully Alan can help you sort this out.
The alternative location for mods, and the one that I think Aspyr have tried hardest to support, is ~/Documents/Civilization 3 Complete/Scenarios/