Defensible housing exists, there have been some viral photos of a few houses that survived this wildfire. But the embers from large fires can fly for miles in high wind, so it would likely have to be the whole city
Not true. Here in Riverside we were watching large still-lit embers floating in (some which caused a repeat fire in the riverbottoms north of the 60, first called Brown then called Holly.) The primary stopping zone currently is around Pomona but another hard uptick in wind and it can easily cover out to the badlands.
These winds are absolutely insane, you just do not understand. When they were peaking on Wednesday morning, my Subaru was being blown almost out of lane while driving down the 91 to work.
If you have fire resistant structures and only vegetation burned, not any structures, it would be much less expensive to replace just the landscaping plants.
In a 80 mph wind, it would be very challenging to design a structure that would survive a wooden house burning next door.