The following Transport Canada document provides an overview of Canada’s Airspace Classification & Structure: T52-4-78-2004.pdf (PDF, 1.12 MB)

In addition the Nav Canada Designated Airspace Handbook document contains information in respect of the designation of Canadian airspace.

The Wikipedia page on Canadian Airspace is also a useful reference.

These are key reference material for commercial UAV operators to ensure they have a clear understanding of the airspace they are operating within.