The reason TPS would request such a thing... As part of the ViClass (Violent Crime Linkage Analysis System) software, there exists the option to input license plates observed at a crime scene. This software allows the detectives to generate a trend chart. That is to say, establish any patterns between license plates, locations, crime scenes. IE, if 5 shootings all have the same vehicle within 2 blocks of it, and said shootings are spread over the city, a trend is established.
Back in the day, a constable would have to manually go around and write all the license plates down. However, with the "street sweeper", the car can just drive up and down a street and it does the same thing.
When it isn't doing this, it's driving around looking for expired tags, stolen vehicles and that kind of thing. I remember reading a statistic somewhere that said it runs on average 250-300 plates a day resulting in a dozen or so violations. That's not too bad at all I'd say...
As for radios, they generally hang out on 69-PKE or 6A-PKE/W, depending on what area they're in.