I'm not sure about full power station's, but; if it is a low power tv station, they are not required to shut off
their analog signal, even if they also broadcast in digital also.
Locally here in Chicago WWME-CA, is still on the air, and to the best of my knowledge, will be for a while.
Low Power TV station's probably have about 2 years before they are required to go all digital.
They made an agreement with two other station's to run their newscast's at 5,6, and 10 PM, and they are
running their own programming the rest of the day. They felt it was important to keep one station on the
air for the people who were still not prepared for the switchover. They are also one of the most powerful
of the LPTV station's in Chicago, with a signal that cover's most of the Chicago metro well.
I think it was a very smart move on their part, although we have known this was coming for quite sometime,
their were quite a few senior citizen's that were not ready.
I just went and checked on an old TV, I haven't used since the switch over, and they are running the news
from NBC 5 here in Chicago and the picture is perfectly clear.