Hi Jason:
I've been thinking about this one. I've come up with two possibilities: Either the DPS is using a conventional VHF/UHF/800mhz frequency/frequencies for this, or they are using the online ticket system over SouthernLinc. My local PD has some MDTs in in a few cars, and they use SouthernLinc to carry the data.
From what I gleamed from news articles, DPS wants to implement a VHF digital trunked system. It woudn't be too hard when that system is fully implemented to have a talkgroup set up for data transmissions.
Warren