The answer to WHY is simply that CHP couldn't get to the other side in time.. I assume you know that area and what it takes to simply turn around?
I watched it both off air, but also on several back haul microwave feeds from the various helicopters in the air, well as listening to CHP ground communications and Air Attack, and that was simply the problem. They had nobody to the north to even think about how to shut it down, and I'm sure that's how it will be defended if it comes to that. Don't forget that fire was moving at 50MPH at times. They did what they could in the time they had to do it. Listening to one irritated eye witness at the south end of the fire when it stretched over 1/2 mile behind him doesn't get even close to the full story. You had a far better recon just watching the coverage from the air.
Charging for a tow is a different story...
More:
For those who,have never seen this area,
HERE is a link to one of the stations that covered it from the air. The burn area is probably close ap a mile long with the two starts on the road separated by ~1/2mile.
I hate that road...