Most public safety trunking systems tightly control what or which radios have access to their systems. Each radio is programmed with a unique ID that the system also needs to have programmed into the system controller. No valid radio ID, no access to the system.
Now on the flip side of this if you get discovered not having a valid ID in the radio that is not in the system controller, you stand a real good chance of having the system "KILL" your radio. Once this is done, you basically have a dead radio. You try turning it on and nothing happens. The only way to recover from the radio being killed is to go to the radio systems administrator and have that person send the "UNKILL" command over the radio system with the radio turned on.
The other issue here is if you have 2 radios with the same ID. If the both come on at the same time and register or try to register as being active on the trunking system at the same time, a red flag gets raised and will show up as a duplicate ID in the system. Again with this ID flagged, you stand a good chance of the radio being "KILLED" or in some places they call it "STUNNED".
Do as you want, but just be aware of how all the trunking systems work. Each different radio vendor handles this a little different, but the bottom line is duplicate or non valid radio ID's will be caught and dealt with fairly fast.