Dude, I got tell you that it's been a while since last time I heard the word mainframe. Anyhow, I don't believe there's a very huge market for mainframes nowadays. You'll probably have to update your skills, but this shouldn't be hard...once a programmer always a programmer.
There might be less positions in Mainframe but the Mainframe-Unix Migration has a great market. TD Bank and Western Canada Bank are using Maniframe DB as Back office DB. Their GPL tables are not getting poulated but these contract based positions are in Toronto, ON. Check the websites and find out that if any Mainframe Analyst position in Calgary. Here it is
http://www.tdbank.com/careers
http://www.cwbank.com/careers
Actually Alberta itself has thousands of opening in various technologies. Best idea will be to find a IT head hunter in Alberta. The Governement of Alberta itself is implementing SAP which is good for SAP consultants.