There are various methods of scanning trunking systems. One of them is to use a commercial trunking radio and program it up on the system. There are challenges that need to be overcome in order to do this, but if you have the resources, it is possible.
What follows are some tips to remember to make things easier/safer as far as having your radio remain undetected, and having to deal with questions from law enforcement if you have run into trouble with them.
One of the foremost things to remember is to ALWAYS set your radio NOT to affiliate with the system at power on, or any other time if possible.
The other thing to do is try and set the radio's transmit frequencies for the trunking system to BLANK, this may or may not be possible depending on radio type.
Something else you can do is: