TEMA comms off of TACN

This morning I've been heaing a decent amount of communications on 158.835.
My questions are; is it just the lower ranking units, support staff that are using the old systems, does it just depend on what systems they decide to check in on in the mornings or what? I thought all TEMA was switched over to TACN and the old system were just back up?

Surely there should be some kind of organization/procedure on who uses the old systems vs the new systems.

TEMA, just like INDHS here in IN, uses VHF to do check ins, and tests and holds that as an backup in case something should go down with the TRS systems. Also, not every County has uses TACN, so TEMA needs to maintain VHF and UHF radios to interop with those County EOCs that do not run TACN radios, during times they do not have patches set up etc.

TEMA has and maintains VHF High, UHF, and Satellite Radios in addition to the primary ops on the TACN. (Satrad to talk to other states EOCs where they are not linked via ISSI on TACN etc, as well as to FEMA HQ) MS EMA (MEMA), uses to also have satrad, and it actually was the primary comm system statewide followed by VHF Low to talk to County EOCs.

Concur they maintain for redundancy and interop the VHF high, UHF along with the TMAC frequencies.
My understanding is they have deprecated the VHF-Lo equipment. Have not heard comms there in a couple years.

Our County has a TEMA 800 conventional repeater link.

It really depends on the individual at TEMA as to what system they talk on. Some use the TACN system, some use the TMAC 800 MHz conventional statewide system and some use the TEMA VHF high band conventional repeaters. It seems most of the people around Nashville use TACN.
The West TN TEMA units use a mixture and they use the TMAC system to make sure the repeaters are in good operating status. The TMAC system is local government's commo connection to TEMA.