I guess we can expect some info about their tricks of the trade at next year's SIGGRAPH. In the past, Pixar and other studios were presenting their tricks in the RenderMan sessions. If you want to use a renderer like they do, I think the free Pixie renderer ia very close match in features. But be prepared, the secret of Pixar's movies is not their software but their scripts and artists (not to mention their killer team of shading and lighting TDs).