I can't speak to your specific situation, however while still living in NJ, near PA, there was one large City that when it switched from a conventional UHF radio system to a 800 mhz trunking system it reprogramed one of it's repeater systems to operate on a GMRS frequency.
I have no official knowledge if the City Administration sanctioned this or not, I was led to believe they had no idea, the City's Communication's Bureau just left one of the old repeater systems in place. A member of the Communications Bureau secured an FCC GMRS License, they basically did everything legit. The original intention was not to be used for on duty communications and the majority of the communications are personal, however I would occasionally, especially at night, hear what sounded like on duty, work related, communications. Not often and I'm sure not officially authorized, but it happened.
Many of the Police Officers and Firefighters were able to get great deals on used equipment that Motorola was taking "in trade"from the City.
Point being, you may have heard what sounds like official communications, but maybe it was something similar to what happened near me. I could always tell the difference between the families and the off duty Police & Fire people by the way they conducted themselves on the radio.