from what ive been reading rebanding has no effect on p25 systems so that is why your scanner is working. just go to radioreference and get the new frequencys.
While that is true for later model digital scanners, it is not correct for the 785D (one with the digital card) or the BC250D (the handheld, also presuming a working digital card is installed; I have a 250D). These scanners are unable to trunk track the 9600 baud control channel used by a pure Project 25 system (in other words, a Phase I, FDMA system).
They will work on the mixed mode Motorola Type II systems, where some (or all) of the talkgroups are digital, but the control channel is still a 3600 baud data stream, the same as an analog only Motorola Type II system. However, should the system reband, and some, or all, of the system frequencies have a zero in the fourth decimal place, then the 250D & 785D would not be able to correctly track the system, regardless of whether the system uses analog, digital, or a mixture of both, talkgroups.