That's just what the law is, best you can do is speak to your neighbour and see if they are willing to help out.
Another quirk off dividing fence law is that if a fruit tree is over hanging into you yard and has fruit on it you are not legally allowed to pick that fruit for yourself with out permission. If the fruit drops you are suppose to put it back over their side of the fence
I have a neighbour who's tree grows close to my power line, rather than get the tree lopper to cut them back he had the tree lopper ask me if I wanted them to do it and pay. I said no, knowing eventually the power company would demand he cut them back
