If the Big One hits San Francisco (spent a few years there as a kid myself, even in a couple of earthquakes) the fire department will probably be forced to use the cisterns anyway.

If I remember correctly, the water mains in 1906 were pretty much rendered useless due to the earthquake. Although we've come along almost 100 years, water systems don't really change that much and are still quite vulnerable to the ground shaking.

As for the high-pressure hydrants downtown, I don't want to be around when one of those puppies breaks loose with 300+ psi behind it. That's liable to kill somebody.

P.S. - If you ever get the chance, be sure to stop by the SFFD museum! Really neat history there... http://www.sffiremuseum.org/