In my business, neighbor and property line disputes are a common occurrence and just a fact of life, but 90% of them are avoidable by simply talking to the neighbor.
It should start with the neighbors. What kind of neighbor does not simply knock on the door or catch up with his neighbor doing yard work and say.. "Hey Joe, I hired a tree guy to trim some stuff so it doesn't come down in a storm and smash into your house"?
A couple of years ago, my neighbor shot me a text... "Having some trees trimmed on the property line to make it easier to back my boat into the back yard. There are couple of limbs from trees on your side I would like to have him trim." "Just wanted to ask if that was OK"
I replied " Thanks for the heads up, no problem"
Came home to the tree guy doing some needed tree work on my property for free. I tried to throw him a few hundred bucks and he wouldn't have it.
A few years before that, opposite side of the yard, a tree came down on the property line, right across my driveway. I saw it when heading out to work, but didnt have time to deal with it so just moved it off the driveway. Came home and that neighbor cut it into 18" pieces and stacked it. I sent him a text to thank him and to tell him I would pick it up after he had a chance to split it! LOL. He would also accept no cash. Both neighbors got a batch of my wife's famous Toll House cookies.
I'm surprised the tree guy was not more proactive and did not try to speak to the abutter before hand...