At the moment, broadcasters do not receive carriage fees for OTA signals. You may recall a bizarre "debate" regarding imposition of carriage fees on OTA signals carried by BDUs (cable/satellite/IPTV providers) last year. Since the largest terrestrial private OTA broadcasters are owned by corporations that also own very profitable pay TV providers, and often pay TV channels, it was a Kabuki performance. The CRTC ruled that the OTA broadcasters and BDUs can "negotiate" carriage fees, so at some point the bills of pay TV subscribers will likely go up $5-$10, probably after the economy stabilizes and the threat of people dumping service to save money is reduced.

Private, for-profit OTA broadcasters live and die from advertising sales. Theoretically, the OTA channels owned by BDUs could be subsidized in slow times by the profits from the pay TV operations, and carriage fees could help relatively independent terrestrial broadcasters cover losses from a lack of ad sales, but I'll let you guess how interested the major players are in funding less-profitable divisions at this point in time.

I'm not entirely sure why CHCH would give up clean reception in Toronto; although their primary market is Hamilton and surrounding areas, their movies, all-midday news, and other programming were more of a draw for me than the fluff carried by OMNI 3 CityTV. While Channel Zero does own some digital specialty channels that earn subscription fees, they're not owned by a BDU AFAIK, so ad revenue is still critical for CHCH.