Good luck with it! Neighbor issues like this are a real energy drain. I hope you can resolve it peaceably. And I agree with the advice given. Most places, IMO, if the plant is over the property line, you are within your rights to trim it. But check that before cutting because there may be local exceptions like greene mentioned.
And talking to the landscapers is a great idea too.
I also perhaps would just leave well enough alone, unless the overhanging branches are actually in the way of something. From the picture it doesn't seem that they are but of course I can't know for sure as I am not there.
