Amazingly, it was just yesterday that I went through all this, and today you find yourself in the same situation.
In my case, this is the best solution -
There are ogg streams for cbc radio here:
These streams play equally well with mplayerplug-in, mplayer, xine.
Other things I tried:
There are urls for all the streams here:
However, I can't play them with anything but xine.
Using the mediaconnectivity plugin, I'm unable to actually play anything from the main cbc.ca radio site (the one where you're just supposed to click on a link, & listen), however, I'm able to get the link info which looks something like this:
and that link will play in mplayer & xine.
To recap, the ogg is the easiest, but you're limited to two possible streams, both eastern, but 32bit stereo.
The scenario where the urls listed in the second link won't play using mplayerplugin (and quite possibly with the gecko-plugin) *probably* comes down to an mplayer configuration issue - I remember in the past having issues, and solving them, but I can't recall what that solution was.
Anyway, hope this helps, ymmv.