CAHSR itself certainly has maps in GIS formats, and could either provide .kmz or provide in a format that could be easily converted if they wanted to. They apparently don't, at least publicly so far, so you would either need to do some kind of workaround based on the PDFs and such that they *have* published or would need to do the FOIA thing. Might be worth contacting them first to see if they can help you? I get the impression that some people have been able to get some GIS data.

If you have something that can work with PDF files as a source then fit them into your preferred projection (some editing required), you could check out their newsroom maps page: [www.hsr.ca.gov]

Some of the stuff in their environmental documents may be cleaner to work with. Also, the construction package descriptions provide a bit more precise information about certain areas.