Federal Conventional Frequencies tend to be shared by multiple Agencies/user types.
Especially in Major Metro Areas.
In the Chicago area, they also have Analog users (Low Power) at the Airports.
This one Freq is used by, TSA, CBP and now the new NAC user, each having their own network and repeater sites
Another example
Here in New England we have 163.7000
with $169 as ICE NAT TAC 1
with $200 as ICE RI/SE Mass Vote Scan
Are you sure those are NAC codes and not talkgroup IDs?
A system is only going to have one NAC code, but can have many talkgroup IDs.