Ive asked TT UK for a Mac version for ages. Nothing came of it though
There are a few ways that you can play TT on a mac.
1. As mentioned , Use Boot Camp to install Xp or Vista
2. Use VMware / Parallels to play toontown under OSX
3. Hope that TT uk will release a mac version soon
Edit : Actually forget Vista, TT UK has problems with Vista , so use XP