If you're in CA I'm guessing that SBC (Pacbell/whatever you know them as) is the local telco that provides the fiber service to your prem. I think you should be able to get diverse pathing from them. It will cost you some $$$, but is sounds like your organization is willing to pay for redundancy. They should be willing to do diverse pathing to your local CO, or diverse pathing to separate COs. You ought to be able to get strands going out of two separate conduits from your building, and completely separate conduits all the way to your local CO, or another nearby CO. You could have a CO SONET node in your closeset CO as well as a CO SONET node in a nearby CO and feed to your upstream provider from there (dunno if your upstream is PBI, which should definately do this, or another provider, who should as well). That way you can set up a healing SONET ring that will survive (in theory) a fiber cut (yes, they do happen. Even in our lovely CA :P ) or a CO outage (as long as your upstream can feed you from both COs). If you have a large enough netblock you should be able to get a connection from a second Internet provider and run BGP with them. Your problem then will be summarization at close by peering point, which is a complexity that you can get around (at a $$$ cost, of course). Just be aware that CO failures, cable cuts, and peering point failures all do happen, but you can always minimize or mostly eliminate if your organization is willing to make a dollar committment to it.

For the record, I am not an expert on this, but I have a bit of experience under my belt.