Is it legal to cover/bury an insurance deductible for an auto collision repair in Calif.?

I'm no expert in the nuances of California law. But I would assume that anything labeled a "cover up" or "burying" certain facts would probably not carry the label of "legal". Perhaps I'm misinterpreting your question, but when anything smells of concealment of any kind, I counsel my clients that honesty and full disclosure is truly the best policy.