This is yet another example of the FCC's increasingly erratic and craven behavior in the wake of the NBP. Applications for channel 51 are frozen, but licensed stations on 51 can continue to broadcast while being encouraged to vacate the channel.
Here is the language of the notice:
"To facilitate the clearing of channel 51, however, we hereby lift the current freeze as applied to, and will accept, petitions for rulemaking filed by full power television stations seeking to relocate from channel 51 pursuant to a voluntary relocation agreement."
It doesn't take a genius to figure that this "temporary" freeze is just a precursor to removing channel 51 from the TV band. We still don't have any predictive models from the FCC on what a re-packed TV band will look like. But that isn't stopping them. They'll get their spectrum any way they can--even if it means doing it one channel at a time.