This is an example of how pedantic California's rules are...
Let's say I own a property somewhere in one of these fire prone areas.
I buy and have available a sprinkler system for my home and have cleared what brush etc., I can under state law.
I then need a fully reliable supply of water to run my sprinklers. The state's laws on rainwater harvesting are such that I can't put gutters on my house and install a say 2500 gallon cistern on my property to store that water. Can't do that. I by law have to let it run off or be used for immediate ground water recharge. So, I would have to buy the water and fill the cistern. But I likely can't install the cistern in any case. It like swimming pools are heavily restricted by building code.
But somehow I manage to get them to let me do one let's say... Now I have to install a reliable on-site power supply and pump system to supply the sprinklers. This too requires permits and inspections and will meet resistance unless I use something like bio-diesel fuel because of environmental laws.
Then there's the sprinklers and environmental laws where I have to have the correct kind of roof on my house to prevent roofing material from contaminating the ground or water supply...
That's how California is today. If you're a millionaire you can probably do this stuff. You're some working stiff that makes decent money you are screwed even if you can do all of this yourself. The state just wipes out your chances with bureaucracy and the cost of that bureaucracy.
Now, if I could install this system, the chances of my house burning down in a wildfire go down by roughly 90%. The state doesn't care. They only care I follow their one-size-fits-all rules and pay for all the permits and fees.
The reason I can't rely on a water supply system like one the city or state has to my house is because in wildfires my neighbors will likely be using it too and the fire department then starts using it so the supply pressure drops to nothing and I get no water for my sprinklers. Hence the need for an independent system with sufficient capacity to go 8 to 12 hours.