From CIC website (this site says I can't post links, so google it if needed)
Performing artists
Foreign artists and their essential support staff, the people that are integral to the performance, can work in Canada without a permit only under these conditions:
    * They are only performing here for a limited period of time.
    * They will not be performing in a bar or restaurant. If they will be performing in a bar or restaurant, performers and their staff each need a work permit.
    * They are not entering into an employment relationship with the Canadian group that has contracted for their services.
    * They are not performing for the production of a movie, television or radio broadcast.
Examples of performing artists who can come to Canada without a work permit:
    * Foreign-based band or theatre group and their essential crew not performing in a bar or restaurant
    * street performers (buskers), DJs
    * a foreign or traveling circus
    * guest artists within a Canadian performance group for a time-limited engagement
    * World Wrestling Entertainment wrestlers (& similar groups)
    * persons performing at a private event, such as a wedding
    * air show performers,
    * rodeo contestants
    * artists attending or working at a showcase
    * film producers (business visitors)
    * film and recording studio users (limited to small groups renting studios not entering the labour market), (business visitors)
    * persons doing guest spots on Canadian TV and radio broadcasts (guest speakers)