Despite their apparent physical similarities, the firmware updates for the BC296D will not work in the BC250D. From what I've seen elsewhere, that ability was disabled in the 250.
Also, the 250 will not be supported for rebanding, and cannot handle a true P25 trunked system with 9600 baud control channels, such as the Austin system. It can only handle the 3600 baud mixed mode (mixed analog and digital) trunked systems, or the conventional (non-trunked) digital frequencies, like what Tx DPS is switching to.The 250 requires a digital card to be purchased separately for any of this to work.
The 296 is on the rebanding supported list, and can handle the true P25 TRS systems, as well as the mixed mode or conventionals. The digital card was included as standard with the 296.