My wife and I spent a weekend at Coos Bay in August, and since she was driving southbound when we went thru the Inspection Station on 101 at Smith River I took the quick minute to look for antennas, and saw none anywhere on or near the building, whose roof make it pretty easy to see from the approach and exit. There's a pole attached to the southeast corner of the building with a security camera and what I thought on our northbound trip might have been an antenna... but it wasn't. Just the camera.
There was a state pickup truck parked inside, but I couldn't see any antennas on it. I agree with your "non-findings" of any radio frequencies licensed to that location, SloScanMan_01. Closest thing is Pelican Bay SP.
The State has done a very thorough job of updating all the CHP radio sites in Del Norte and Humboldt counties in preparation for the CHPERS changeover, including two scalehouses within about 5 miles from where I live and which I've seen open perhaps three times in the 21 years I've lived here, but they have no licenses in the area of the border station. Perhaps they rely on mobile radios if they need to call somebody. I don't remember ever seeing more than one worker on duty at that station, which we pass thru a couple times a year.