I have no need to become an expert on California property law, but the exclusions at your link are very narrow. This related page discusses the transfer of ownership interest in a legal entity that owns California real property. triggering a reassessment.
If the originator of the trust maintains a controlling ownership in the trust, no sale has taken place. If they transfer control of the trust, the page I linked says that triggers a reassessment.
http://www.boe.ca.gov/proptaxes/leopcio.htm
I wonder if it frequently just isn't worth unwinding the corporation.