I asked my son-in-law who plays gigs with a bluegrass band (he is a consulting engineer by day) what the rules are. He said it "depends." Many musicians will not play with non-union players. Many clubs are only open to hiring union musicians. Work for any event covered or hosted by the CBC (Canadian Broadcasting Corp., a government network) requires a union ticket. You can usually play in rural areas without a ticket, but members of his group have tickets to avoid problems.
No one under the age of 18 (must have ident. card) is allowed in any public venue where liquor is served.
Busking in Calgary is by city approval only.