i don't think the insurance policies are for actual replacement cost. i suspect if the hill had to be rebuilt.. it would never be built like it is today.
all of the towers on wilson are free standing and do not have guy wires with the except of the old kcbs-tv 2 tower that is nearly 1000 feet. if that thing were to fall the wrong way i don't think it would hit anyone else.
usually what happens when these things go bad, is the coax melts or catches fire, which can often screw up the transmitter. the fire runs up the coax and seriously f's up the antenna. then if things really go badlly, you somehow get the building structure to catch fire and its a start over scenario with an existing tower.
my guess based on having done this for eternity... would be worst case you lose a couple of structures and antennas. the rest of it survives and this isn't too bad.
if it were to really go to sh*t, the heat from all of the fires converging together at the top would just start setting everything around it on fire that wasn't concrete or metal. in that case we probably have a pretty grand mess. probably less than a 1 percent chance of that.
in that case you hope for a surviving tower and some people down the hill with alot of backup equipment and some generators.