So another hypothetical question. A volunteer fireman carries a radio issued to him. It's been programmed by the state to receive and transmit on fire channels for his area. It's issued to him in his name to carry. Could a buddy who's a radio tech for the state program other receive only channels into his friends radio without the state knowing he's listening?
Not on a trunked system. They would still need the system key.
If I recall correctly, some radios won't let you mess with anything if you don't have a system key.
Other radios will let you change the non-trunked channels.
Also, remember that on a multisite system, NAS isn't going to work very well since the trunked system doesn't know that the radio is there and won't send traffic to the site. No public safety agency/employee should ever be relying on NAS to do their job. That's just idiotic. Any agency that needs access to a system/talkgroup needs to go through the proper procedures.
Like in my previous post, not asking would or should. Simply could. Thanks.
There's a lot of variables here and hypothetical questions that don't provide details are going to be difficult to answer accurately.
"Buddy" or not, there's some FCC rules that get in the way, and as suggested above, a -real- radio tech that wants to keep their job would probably not do stupid @$$ stuff like try to do NAS on an agency radio, add channels, or change anything without approval.
You will sometimes see wannabees/YouTubes experts try to mess with agency radios and often it doesn't go well.
This is one of the reasons why I password lock the read and write access to the radios. No one outside needs to be messing with the radios.