Outsider? I spent over 3 decades in law enforcement. I'm certified to train National Incident Command and have been a part of Homeland Security since 2004. I'm a certified law enforcement instructor, a certified fire instructor and a certified arson investigator. Even though retired, I still manage a 40' mobile command vehicle with almost more radios than I can count There are radios specifically programmed with NIFOG frequencies but no body uses them. I drove that bus to Pearl River County, MS, after Katrina. We spent over a week there and managed 6 other agencies and no one had NIFOG frequencies. That bus has been to a lot of train wrecks, tornadoes, hazmat situations, etc., and no one except us has ever had NIFOG frequencies. Even so, everything worked fine. The only time I've ever seen NIFOG frequencies used is during training exercises.
The key word here is "interoperability." Within our jurisdiction, we don't use NIFOG frequencies because we don't need them and we can label the talk groups on our own radio system anything we like.
I may be a lot of things but "outsider" isn't one of them.