the original NPSPAC freqs were required by law to be abandoned, so they had to reband them or decommission them. so yes, it was either reband or "give" them back. it does not matter what the future intentions were for the system, Nextel had certain obligations under the rebanding order and they had to pay for all costs of rebanding any affected licensees. i've personally been involved with several rebanding projects in both the original move back in the 90's and the current one. if the system was on the air and operational, they had to pay to reband it unelss the owner decided to just shut down and cancel the license.
they can use the rebanded freqs with the digital system, they may have just not put them in service yet. or they may decide to make them a conventional system for backup/special event use.