I don't remember Expos having an encryption option, but that was a lot of years ago. CBI was licensed for 155.460, but I suspect they also had some of the other CSP freqs for using where CSP didn't.
It used to be (and probably still is, though I haven't read the rules in a while) that for surveillance operations an LE agency that otherwise has a license could operate on any of the PP frequencies at less than a watt (or something like that) without a specific license. That was back in the VHF/UHF days. It was mostly to allow for body mics, but some small handhelds were also used that way. Don't have any direct knowledge of how CBI operated, but that was typical for a lot of LE agencies in the 80's and early 90s.