Municipal fence rules and neighbour cost-sharing are different questions
A city can usually tell you whether a proposed fence complies with local height, placement, material and safety rules. It may not decide whether a neighbour must contribute to the cost, who owns an existing fence, or what happens when neighbours disagree about replacing it.
Do not assume there is one Canadian cost-sharing rule
Private-law rules differ by province and the facts of the property. Local bylaws may also address maintenance or line fences differently. Before relying on a cost-sharing claim, identify the province, municipality, exact property line and any agreement already in place.
Agree on the project before money is spent
If both owners want a shared fence, write down the proposed location, height, material, finished side, contractor, total price, each person's contribution, access arrangements and responsibility for future maintenance. A short written record can prevent a later disagreement about what was actually approved.
Keep the municipal compliance issue separate
A neighbour's willingness to pay does not make an over-height or unsafe fence legal. Likewise, a municipality's approval does not automatically establish who must pay. Resolve both tracks before work begins when the project depends on cooperation.
When the dispute is really about the boundary
If the disagreement is over where the property line sits, do not solve it by moving the fence until the boundary is established. Survey evidence may be necessary. For a significant financial or legal dispute, province-specific legal advice can be more useful than a municipal fence counter.