Yep. I have BGT installed via Wineskin with several mods on Mountain Lion. The key is to use Windows versions of the mods. Easiest way is with BG Mac mod installer v2_1.app. Even widescreen mod works. A couple of mods require the wineskin installer to run instead of the app. Everything works flawlessly on my MacBook Pro.
My game is extremely laggy, I know its not a problem with my system as I can run SC2 fairly well. What type of Wrapper do you use? Do you have anything special about it?
Not sure if this is helpful, but I successfully run all the infinity engine games fully modded on Linux using wine. As shylaman says you just need to install and use the windows version of the mods.
Comments
http://www.paulthetall.com/baldurs-gate-2-mac.html
http://forum.baldursgate.com/discussion/17717/tool-easy-weidu-mod-installer-for-os-x