To answer your first question, you can go to this link and enter your address and it is supposed to tell you the fire hazard for that particular spot: http://www.mofd.org/fire-prevention/do-i-live-in-a-very-high-fire-hazard-severity-zone . Obviously Orinda is a wooded community with hills, narrow roads which can make it more prone to fires, but the Moraga Orinda Fire District has an excellent reputation. There was a recent fire in a home where the occupants had taken the smoke detectors down to replace the batteries but never re-installed them, not a good idea.
As for the condition of the gas lines, you can track the progress of PG&E on repairing and upgrading the gas lines here: http://www.pge.com/progress/
I have an original Frank Lloyd Wright designed home for sale in Orinda and while it did have a fire in 1995, caused from a space heater, it has not been harmed by any other wild fires since it was built in 1949. So in my opinion, Orinda is just as safe a place to live as most cities when it comes to fire danger.
Oh yeah, one last comment, today happens to be a Spare the Air day so no one is allowed to burn fires at all, so today is actually more safe than most!
I hope this was helpful, let me know if you have any other Real Estate related questions.