Its secure data and voice, so the it wouldn't matter.. you can't listen...
I know I'm replying to an ancient post, but the above response is quite wrong. It can matter a lot.
For OPSEC reasons, they try to maintain a very low profile during the movements. Hearing secure, simplex traffic on a radio freq known or suspected to be used by DOE OST, especially when not near a DOE/NNSA facility, provides a good indicator that a movement is in the area.
Their HF & SATCOM have a low probability of detection, but the VHF system used between the security escort vehicle & materials transport vehicle is not.
I live along a transport route, know the primary freq, and thus it is a signature that let's radio-geek me know when they're trucking goodies through my area, even though the comms are secure.
