That's an inovative use for subchannels if ever there was one.
Instead of soap fans (hate 'em. The soaps, not the fans

) having their programms interupted by the government or news flashes, they could just tune to the subchannel to watch the show in it's intirety.
Weather alerts? Put a crawl at the bottom of the screen to warn viewers instead of interupting the program with live doppler or whatever.
Sounds like a win win situation for the viewers.