In the event of conflict, the Civil code deals with parts of this problem in article 1002 et seq. Certain choices are offered to you. You can decide to install one to your liking on your land and at your expense (Article 1002 Civil code),and the neighbour can't object except with regards to the municipal bylaws on the subject, or to the height of the fence. Make sure to have the necessary permits from the City to carry out such a construction.
The Civil code provides another option, i.e. the installation of a fence on the property line between the two pieces of land. In this specific case, the law provides that the two neighbours should each pay one half of the cost of the fence.
If you want to install a fence on the property line without first agreeing with your neighbour, you will need to ask the Court for permission to install a particular model of fence, and obtain an order forcing the neighbour to pay you half of the costs. Thus, you will not be able to install the fence with first obtaining a judgement from the Court against the neighbour, or claim your costs back from them, or by notifying them in writing. Indeed, this procedure is designed to allow the other party, or the Court, to have a say on amongst other things, the costs and features of the fence. The position of the Courts on this subject has been consistent insofar that the neighbours cannot take the law into their own hands by proceeding without agreement or authorization, as this would be deemed to be an abuse of right (1).
The owner who acts unilaterally will ultimately suffer the consequences of this and will have to pay the whole cost of the fence even if it is on the property line.
In any event, before making a decision and spending money, we recommend that you consult a lawyer.
definition: «property line» a line which separates two lands and which belongs to different owners.
1. Collin vs. Guindon et al, 540-32-019263-076, Laval