The use of any encryption on primary dispatch or interoperable talkgroups is concerning as that use is against the recommended protocol/standard for encryption in the MRAM Radio SOP.
Either...
1) The MRAM Radio SOP does not apply to Williamson County.
2) The Encryption Standards have changed.
The well documented, established and published MRAM Radio SOP Encryption Standards section recommend the following protocol/standard:
Metro Emergency Radio Management Committee (MRAM)/800 MHz Radio Systems Standard Operating Procedures:
Nashville > Information Technology Services > IT Services > Radio Communications > Metropolitan Radio Management Committee
It is possible that Williamson County falls well from the original definition of "outside agency participation" which must adhere to MRAM Radio SOP. Possibly like other more recent entities like Mount Juliet and Goodlettsville with their own tower sites and frequencies, have more leeway in their participation and own standards.
Also possible the Encryption Standards have changed, which could allow further encryption changes for other system users. Would expect however the latest MRAM Radio SOP to be published and reflect any changes.
Considering the change from Metro Radio to Middle Tennessee based system, possibly MRAM disbanded and/or SOP no longer in place at all. However beyond here on Radio Reference and a mention in news article of becoming a "Middle Tennessee" system, I am finding no governing body change or other documentation to indicate such a change. IE Mayor Briley last reaffirmed all Exec Orders from Mayor Barry, including
Executive Order No. 019 — Metro Emergency Radio Management Committee.
In today's current radio climate--to support interoperable communications, for the purpose of media access, and for promoting the spirit of general government transparency and openness--excessive use of encryption should be avoided, especially with routine dispatch communications. Up to this point the agencies using Metro Radio have demonstrated a good practice standard approach that meets that expectation.
If an agency receives the various financial, technical and logistical benefits from sharing Metro Radio assets, I would expect that agency should align with and be expected to follow Metro Radio practices and standards as well.