It's my understanding that Canada Post tried to resolve this issue diplomatically through the Universal Postal Union. It is a body of the United Nations that brings together postal administrations from around the world to look at issues like privatization, public services, deregulation, exclusive privilege, and the universal service obligation. So it's my understanding that Canada Post did try to resolve that issue through the UPU. When they were unable to do so, they resorted to the courts.
On March 26th, 2007. See this statement in context.