Honestly pretty damn secretive. I worked at Google for the summer and that was the only building on the campus I couldn't go into (I could even go right up to Larry's office door but not to X). My good friend was an intern on X and he never told me a word about what he worked on or who he worked with. That's just an intern. So even though they do reveal some projects for PR once in a while, it's definitely a very secretive part of an otherwise fairly transparent company.
He was a student at a design school (I believe it was the Art Center [1] in Pasadena). Incredibly talented at designing cars and also an insane work ethic. 99% sure he was on the self driving car project as an industrial designer but he never confirmed. He said they came to his school to find someone. For a normal job you can go to Google, but from what I've heard Google X comes to you. They know who they want.
