Definitely looks like a radio antenna, so they would not want plants blocking the line of site. Mounting at the highest level and clear of obstructions, would likely give best performance so may have been reason for choosing location. I think that some utility providers have the right to install their equipment where they want without planning permission, although I may be wrong. They may have given notice and sought consultation by placing a tiny notice in you local paper, or pinned to another pole half a mile away?
I genuinely wish you luck, your moral case is strong but I am not sure about your legal case.
