Yesterday I could test EOS Utility 2.11.0 which comes with the 5D MK III.
The installation went fine and the program opens without crashing. My 5D MK II was recognized also without crashing. But when I connected my 1DX the message comes that an unsupported camera was connected. So it looks to me that you need a greater version than 2.11.0 to use the EOS Utility on Mountain Lion and the 1DX.
Are the Versions 2.11.1, 2.11.2 or 2.11.3 officially released? Do they work on ML? The actual 2.11.4 (which comes with the 1DX) crashes in Mountain Lion :-(