In Aurora/Newmarket/Bradford there is no hard rule whatsoever.
If your neighbor doesn’t want to pay they won’t.
If they refuse you can build it inside your property (6 inch’s from property line) and paint it like green on your side if you like.
I just replaced a 20yr falling down fence and our neighbors were being dicks about it.
You can see that I only replaced what was important to me seeing as how they didn’t want to contribute. I replaced what was on my side of my hedge. cheap neighbors.