For the past two evenings, I've been hearing chatter on the DPS Ch. 159.09. The readout indicates "CLE-RPTB", which I assume means Repeater B. Yesterday, it sounded like they were trailing someone, keeping track of where they were, but then I will hear just some chatter like car to car "shooting the breeze", as we used to hear on the old Ch. 3, 154.95, I believe it was. I know I have never heard this frequency used for as long as I've owned this old GRE 600, since getting it in 2012. I will definitely be keeping my ear open to see what else they have to say on this channel.
"CLE-RPTB" is the Texas Rangers, the investigative branch of the Texas Dept. of Safety (DPS).
"CLE-RPTA" also part of the agency, using their long-time 155.505 Vhf-high channel.
The Rangers often work investigations for criminal activity that spans several counties, requiring surveillance to build a record of the violations and collect evidence that could be used during the prosecution of a criminal case.
You might also find them investigating improper or illegal conduct of a governmental figure. Quite often, the agency is called in to investigate other cases, such as an officer involved shooting, to ensure that a fair & unbiased review is accomplished. That was the case here in Dallas, when an off-duty officer mistakenly shot and killed someone she thought was an intruder in her apartment, when in fact, she was the one in the wrong place.
As Tom has noted, it's best not to post about surveillance operations. It could affect whether the investigation is successful, as well as encourage the agency to switch to encryption.