Say that I am towing my friend's new travel trailer with my pickup and hit a low hanging tree limb and destroy the trailer's electric awning. Whose insurance pays, minus the deductible, of course. ...
my car insurance covers liability and property damage of MY trailer when I am towing it. Trailer insurance covers collision damage to the trailer, comprehensive etc. and liability when the trailer is unhooked.
Now, if I'm towing someone elses trailer, interesting question. probably varies by insurance company.