You can get humane traps from the city animal bylaw place and capture them, bring them back to animal services (in inglewood) and the owners will have to pay a fee to get them back. i think there is some sort of bylaw pertaining to cats being a nuisance to neighbors. not sure if there is a charge for the cage rental though.
http://content.calgary.ca/CCA/City+H...erest/Cats.htm