audio sub-channels only run at 0.2 Mbps (200 kbps), and ATSC has built-in support for digital SAP...and for audio-only subchannels in digital stereo, too (though those start at x.50, and i assume they can go only to x.99), using that for an entirely different feature (like a radio station) would be wasteful, especially if there's a large non-english-speaking population nearby.
The Weather Network, CBC NewsWorld or CTV News Net as sub-channels? would be great, but it'll never happen...
What needs to be done for the CBC to start saving money is to automatically merge its two networks (CBC English and CBC French/SRC) together, with x.1 being English and x.2 being French... in areas with large French populations, Quebec, and New Brunswick, it would be reversed. They could shove two HD signals in, 720p60 at 16:9 with just a bit of room to spare, and there would still be absolutely stunning picture for both (provided another sub-channel was NOT in place).
This would also apply to the OMNI stations and possibly (C)[T]\V/ with its relationship to /A\ (why not re-brand it as "Eh?" while they're at it?
one thing i don't get is that CTV and Global are so firmly against the cable companies, yet they want to do away with over-the-air and go cable-only. not thinking things through.... or do they want to start their own cable/satellite systems?