As I heard it, the author of SB 100, California Senator Johannessen, is a real car guy who pushed this bill against great resistance in the state Senate. The only way he could get it through at all was to include an annual cap on the exemptions issued. It never would have passed at all otherwise. Or so I have heard.
To your original question, I would say it is not difficult to register a Caterham 7 in California in full compliance with the law through the SB 100 process, if you do your homework up front. However, the 500 car limit is currently woefully inadequate for the number of applicants, so it can be a bit of a lottery. Preparation is crucial.