The traffic squad division uses them for their primary communications. They are a separate unit from the troops of that district that does speed checks, traffic law enforcement on the highways and other details like DUI check points (usually they control the operations). Each traffic squad has their own frequency (1 is western district, 2 is central district and 3 is eastern district). Most of thier communications are with the "message center" at CSP HQ in Middletown though each troop can listen into their district "traffic channel."
That is how it was set up when I was still dispatching for CSP, things probably have changed greatly since I left.