You will need the libraries for iray that are included with licensed copies of 3ds Max 2014 or mental ray Standalone
iRay is the Mental Ray interactive rendering environment that leverages the parallel processing capabilities of CUDA. As noted in the post, the steps will work for Maya 2014 on any platform, osx included, however, you do need some files that are included with and exist only with licensed copies of 3ds Max 2014 or mental ray Standalone.
Essentially the process is broken down into two steps, where you move the files needed to the proper location, and then set the string options on a per-scene basis using MEL.
check out the tutorial for Setting up and using nVidia iray in Autodesk Maya 2014 here.