Also note: THP does have and use encrypted TG's. So your scanner may not unmute on those when in use. I set my TRX-1 to do the "Busy Signal" tones on E TG's that way I know if they are in use and can log UID's etc...
I do hear THP-D4-Disp1 everyday that I am listening to the scanner, mostly through Arlington but occasionally through Memphis THP HQ. I last heard them as I type this response from the Arlington tower.