
That is why I planned ahead...
I live here in Idaho where (even after asking my local P&Z) we have no rules or guidance to go by for PV. But, when I placed my cells I took into account my neighbors aspen trees before I chose my angle and location. At the time the trees were only 15 feet tall, but these trees get 50-70 foot tall and with the sun at 15-18deg at the highest in the winter months this was quite a restriction on me. I never once considered my PVs should trump their property rights.
I'm betting the shade lost by removing those trees will increase his/her A/C needs by the summer sun beating down on their roof.