I believe that what we've all been hearing on SPEN is nothing more than people screwing around with their radio equipment.
I've been a 9-1-1/emergency services dispatcher for 16 years now and have seen dispatchers playing with the radio equipment, exploring functions on the console that are not used in regular day-to-day operations, if they're used at all. Our consoles are from Orbacom and have several paging/DTMF functions that my department does not use. Yet by playing with the keypad you are able to transmit those tones over whatever channel is selected on the console.
Radio immaturity on SPEN is a big problem. For those who don't know NJ has a statewide set of 4 frequencies known as SPEN-Statewide Police Emergency Network. It is more commonly known as the Statewide Police Entertainment Network. It is intended for communications between agencies but it is more often used as a radio playground.
Dispatcher professionalism is another topic entirely, and one I won't get into here, suffice to say those who play on SPEN are NOT acting as professional dispatchers.