http://www.calgary.ca/DocGallery/BU/...res/fences.pdf
Information on Land Use Rules for fences. Worst case is if by-law officials come by they can order the removal of the addition to the fence. For them to come by most likely someone would have to complain. In most cases you are given a dead line to remove the construction and if it is not removed then the city will impose a fine. Not sure how much the fine is.
Also if you wish to build a higher fence this is the application requirement list:
http://www.calgary.ca/DocGallery/BU/...relaxation.pdf
Also if you have a copy of your Real Property Report you can see for sure whos property the fence is actualy on. Very often people assume it is on the property line but it very rarely is directly on the property line.