I don't get it then, so explain it to me.
Local channel 4 - the ABC affiliate, for example... could stop broadcasting signal today and be cable only if they want?
The way I understand it H.D. is that all "analog" signals, i.e., those that you now received over your T.V. antenna and FM and AM antenna, would be digital only. The "band" those frequencies lie in would be relegated to "digital", i.e. ones and zeros. When you tune your new car tuner into your favorite station, have you ever noticed that the music, artist and song name is displayed....this is a digital signal transmitted along with the old analog signal....I can pick up the audio on my old '85 Jeep radio but I have no display, just music. If this is approved, in 2009 my old Jeep will pick up nothing, the analog signal ceases and the new digital format is all that is transmitted..... In a nut shell.
Yes. Assuming they think they can explain their actions to all the commercial advertisers that paid for time slots in specified viewing timeframes and dates for contracted lengths. If they can swing it and convince the sponsors that going off the over-the-air broadcast frequencies to another area entirely, that is entirely within their prerogative.
Of course, I would not recommend such an action to any company as a here-today-gone-tomorrow change. More likely a period of months if not years with an overlapping timeframe of dual broadcasts in the old and new mediums to allow viewers to adjust would be called for, then ceasing functions in the old medium. Assuming the company actually wishes to continue as a viable BTV (Broadcast TeleVision) company, that is.