Although this does not directly answer this question, the CRTC website shows a history of broadcasting in Canada, including: 
 *1928: The Commission recommends the creation of a Canadian broadcasting network, to be supervised by an independent federal agency. 
 *1932: In response to the Aird Commission's report, Parliament sets up a special committee on broadcasting and acts on its recommendations through the  Canadian Radio Broadcasting Act. This legislation, amended in 1936, creates the Canadian Radio Broadcasting Commission (CRBC). The CRBC is to regulate and control all broadcasting in Canada and provide a national broadcasting service.   
 *1936:  Amendments to the 1932 Canadian Radio Broadcasting Act create a Crown corporation: the Canadian Broadcasting Corporation (CBC). The CBC is now responsible for providing a national radio service in Canada. The Corporation produces, broadcasts and regulates programming. The CBC replaces the CRBC and takes over the Commission's staff and facilities (8 public stations, 14 private stations).  
 *1937:  Through the Minister of Transport, the CBC organizes the Havana Conference attended by the governments of a number of countries in the Americas, including the United States, Mexico and Cuba. They reach an agreement, called the "North American Regional Broadcasting Agreement (Havana Treaty)", on the allocation of frequencies. This will reduce interference. Under the Havana Agreement, Canada obtains six unoccupied frequencies as well as other limited or shared frequencies. These new acquisitions enable Canada to introduce more powerful transmitters and expand its network.  
 Another site that gives some information is CBC Radio-Canada French Radio Network history. It states: 
 *1937:Radio Canada changed its call letters from CRCM to CBF. On December 11, the French language CBF Montreal station was officially opened and it operated on 50,000 watts of power at a frequency of 690 kHz, thereby laying the foundation of the Radio-Canada French language radio network. The Federal Minister of Justice, Ernest Lapointe, and the Minister of Transport, C.D. Howe, attended the station's inaugural gala that was marked by a symphonic concert, excerpts from a few legendary operas and a number of traditional sketches. Paradoxically, "CBF" were not radio call letters that had been officially allocated to Canada, but had rather been assigned to Chile. CBF is the acronym for "Canadian Broadcasting French". An agreement had been reached between Chile and Canada regarding the use of these call letters, because there was indeed an "authentic" CBF in Chile, but it was a Chilean Coast Guard radio station. 
 Hope this helps lead someone in the right direction; I'd really like to know the answer to this question!