The CA FAIR plan is most common in high risk areas, that no one else will insure. In those areas, it's usually by far the cheapest coverage (though still not cheap, because it is high risk). I know it doesn't cover long term vacant or unoccupied homes.
You'd be best off speaking with an insurance broker. I use one that's incredibly knowledgeable about FAIR as a lot of the loans we have closed together are in such areas (wildfires mostly for us). Feel free to reach out to me privately if you want his info.