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. ...
Why would you even get your friends insurance involved? When you do that, his rates go up. Are you going to pay him when his insurance rates go up for a year or more because of your mistake?
It's your mistake. If your insurance doesn't pay then you pay out of pocket to make it right.