As CNN, and CNN HD, is free to air on satellite, I suspect BT aren't paying an awful lot, if anything, to supply the channel. You may just be better off hiding the channel if it means that much to you.
I can see CNN being the start of other news companies going on board such as France24, Bloomberg etc.
I do hope so, but HD would be nice. Seems a little archaic to be launching anything in SD these days.