The phone screens were conducted by engineers from different areas working in similar roles. Each phone screen was about 50 minutes. Each started with time for me to ask as many questions as I wanted about Google and the role I was applying for. Then when I was finished with those questions, I was asked to describe my experience, interests and accomplishments. Finally we finished up with about 20 minutes of technical questions that seemed to draw primarily on the programming languages I had listed in my application.
A few examples:
1) How would you implement garbage collection in C?
2) Describe one of the software engineering design patterns.
3) How would you extend Array in JavaScript so that it could add all the values stored in an array? (An exploration of Object prototypes, which demonstrates the level of sophistication with the language.)
The engineers were very eloquent, not at all pretentious and highly knowledgeable. It didn't work out, but I learned a lot from the interviews and was exceedingly impressed by the engineers there. The role wasn't a great fit for me anyway and I intend to try again in the future.