Urs Holzle, Google's Senior Vice President of Operations, answers questions from Rich Miller of Data Center Knowledge in a piece titled "How Google Routes Around Outages".

http://www.datacenterknowledge.com/archives/2009/03/25/how-google-routes-around-outages/

Postmortem of the February 2009 gmail outage (pdf): http://www.google.com/appsstatus/ir/1nsexcr2jnrj1d6.pdf

Thanks for sharing this, we rarely see answers to this type of questions.