The last I heard, they were on an OpenSky trunked system.
OpenSky systems cannot be monitored by any scanner. That's probably why no one has ever posted any info.
If you go to the FCC ULS page, you may be able to do a search and find out what frequencies they're using. I don't have a smart phone, let alone a computer, to do it myself.
FWIW, the Central Arizona Water Conservation District, which owns and operates the Central Arizona Project (CAP) Canal system, is also using OpenSky (per the Southwest Frequency Directory, 10th Edition, circa 2009). The frequencies listed for them include 866.4125, 867.5625, 868.1125, 868.5625 and 866.3875. As of this wrting (typing) two of them have an active CC.
John
Peoria