FYI, there are protocols for EVERYTHING in the fire service. As far as justifying the $20K bill, that is not my problem, it is between the homeowner and the fire company.
As I have said, most likely the fire company will accept whatever payment the insurance company offers to pay as homeowner insurance rates are based in part on the ISO rating of the property. In this case there is no fire protection, so that homeowner will have the highest possible ISO rating. However, ISO ratings mean nothing to homeowners that don’t for whatever reason have homeowners insurance.
I know, I was a VFF for 15 years.