It probably wasn't exactly rebanding, but is related to the build out of the system in the Troop B area. Apparently upgrades to sites across the state have to be done and they are going to try to do them at the slowest part of the day.
There is a related Troop B thread in this forum, you should take a look at that.
ReBanding has been occuring for months with Troopers scheduling to bring in their Cruiser and Portables to the ReBanding Centers for reprogramming and/or replacement.
What occured at 0400 was the Network was taken down for some of the work to begin to migrate the new P25 B Troop system into the legacy Analog network. It is likely a few more of these network disconnects will occur over the next few months.
As for the existing system. No channel changes have occured except MA-DOC [800 TRS] and some of the 800 Simplex and Interops [ITACS to 8TACs]
The way rebanding works (per the Subscribers' Guide) is as follows:
First, you upgrade your subscriber units to rebanding capable firmware and your software to rebanding capable CPS.
Second, you reprogram all of your subscribers with rebanding-specific data (leaving pre-rebanding data also in place). This is usually limited to control channel frequency changes and failsoft frequency changes.
Third, you modify your infrastructure hardware as needed (re-channeling control channels and voice channels) and you inform your controller that rebanding has been accomplished.
For scanner listeners, rebanding has two implications: you have to modify the frequency assignments for any control channels that are changed by rebanding, and you have to modify the channel number table that the radio uses for converting the integer "channel numbers" issued by an OSW. Note that this is only required if after rebanding the system will use a voice channel for a frequency that is not covered by the "old" channel table.
For most of the MSP system, specifically the A/H zone, control channels need not be changed and the "old" channel number table will continue to work.