167.75 is main federal LE interop tac channel

from page 23 of 192 of the 2021 NIFOG .... "In practice, ESF13
primarily uses LE7 as the standard Federal LE interop channel between
LE units"

LE = law enforcement

my translation ... when there is a major disaster, and Emergency
Support Functions are activated, federal law enforcement units
primarily use 167.75 NAC 68F for car to car interop messages at the
scene ... for example ... if a group of FBI agents and a group of
USFS law enforcement agents are doing security work at a large
disaster, and they dont have any channels in common that can be used
for intercommunication, then they would use 167.75 to talk to each
other

note ... this info is not mentioned at
https://www.radioreference.com/apps/db/?aid=7742 ... the list of
nationwide interop channels