I can cook up a pile of reasons for the unfortunate lack of subchannel use by the Canadian broadcasters.

1) Fulfilling CanCon requirements is probably a concern, although anyone operating in Canada knows they either play by the rules or answer to the commissioners, and unless there's an odd quirk or gap in the regulations the licence holder should be ultimately responsible for everything carried on their signal. It's not as if there is a lack of content available to fill airtime, though if you want *quality* content, that may be a different issue :).

1b) Re: offering a digital specialty channel such as CBC News Net on a terrestrial subchannel, I wonder if there's a concern about the terms of the licences those channels operate under, and what may have to be changed - legally or content-wise - to offer specialty channels on OTA. The audio portion of CP24 is broadcast on AM 1010 in Toronto, but I'm inclined to dig through CRTC filings, looking for what (if any) applications had to be made. If the licence holder didn't deal with the commissiom at the time of the switch to the CP24 feed, I'm positive the issue will come up at the licence renewal for the AM channel.

2) Speaking of content... there's just not that much in terms of terrestrial content carriers aside from the big five (CBC/SRC, CTVglobemedia, Rogers, Canwest, Quebecor), and until someone new is willing to make the attempt, it just won't happen. I guess one of the independent stations could do something, but given their more limited resources it would be a serious gamble, particularly now.

3) The major terrestrial broadcasters are, except for CBC, owned wholly or in part by companies that have large, profitable broadcast distribution undertakings (aka cable and satellite). At the moment, they have no reason to offer even ad-supported specialty channels on OTA or otherwise spend money on broadcast channels they can't charge subscription fees for... yet.

Going off-topic here: Incidentally, that fee-for-carriage Kabuki theatre of months ago continues to tick me off, for precisely this reason. In several cases, entities on ostensibly opposing sides of that "debate" are owned by the same parent company. Even accounting for internal conflicts, the entire mess reeked of collusion; it's pure profit for the parent company, as the BDU owners will just pass the cost of the fees - which they get to decide upon, with CRTC blessing - to pay TV subscribers. As a final insult, CBC threw in with the openly pro-fee parties, and found itself excluded by the CRTC from being able to receive any fees that are imposed!

Back on topic (and off my soapbox...), I wouldn't expect any movement on the Canadian side until the digital switchover is completed, and even then I'm not holding my breath waiting for fresh content from the big players. It's too bad, as I've come to enjoy the American subchannels (in particular, Universal Sports on occasion and ThinkBright). I don't think much will happen until someone, government or industry, tries to take on the media oligopoly and shake things up.

rant mode off, finally.