Well after changing all of their stations twice over the past year, it appears that their direct streams no longer function. This doesn't appear to be specific to Montreal. The URLs listed at http://www.cbc.ca/listen/includes/directr1.html
don't appear to work any longer. Although the flash streams at http://www.cbc.ca/listen/index.html
seem to work, flash based streams won't be playing on the Soundbridge under any foreseeable circumstances.
It may be worth your time to contact CBC directly and ask them if they intend to allow the direct MP3 streams at the first URL above to work of if they will be doing flash only in the future.