The Canadian Content regulations of the CRTC (CA Radio Television Commission- hope I have that right, I never remember abbreviations) are on a precentage basis. I think this is what Art meant; 'part of every hour' would mean truncating certain programs and/or compositions.
Of course the regulations are imperfect; certain popular Canadian stars who have made it on the 'world' stage are heard too often and others are ignored by commercial Canadian broadcasters.
The regulations support Canadian content, not just music but talky-talk as well.

The national broadcaster, CBC, has two domestic services, French and English. Primarily Quebec-based, the French service is not listened to by English-speaking Canadians, and vice-versa. Except for the aforementioned 'world' stars, Quebec performers are unknown in commercial broadcasts in English-speaking Canada, and very rarely played in the CBC English broadcasts.
There are other complications.

These comments are largely digression, but those interested in the CRTC regulations will find them here: www.crtc.gc.ca/ENG/LEGAL/Tvregs.htm