Riverview IS a pyschiatric hospital for children/youth. It is a state run facility -(DCF). They run a DCS on that frequency, I remember picking it up one time, Just don't remember what exactly that DCS was. They do run low power. Their radios aren't used for a whole lot except like someone mentioned, transporting patients from unit to unit, or to the west or east gyms and such like that. Basically whenever a staff leaves a unit, they bring a radio, first they turn it on and do a radio check though. Occasionally they will call for assistance over the radio during a "psyc emergency". They have a system there where they can just push a red button on the wall and blue lights go off everywhere in the building. at that point, Pretty much every staff member checks the closest "alarm panel" and it displays in text format where the emergency is and a summary of what it is.
Not sure if they still do, But they used to use those radios quite a bit, Albeit for fairly mundane activities.
Best times to hear them on the radio would be between 7:30 - 8:45AM (Waking up, Getting the children to school) or in the area of 3:15:4:45 (Afternoon recreation, Dinner). Also try 6:15 - 7:45PM (Even recreation).
Every unit that brings any patients to any of these functions, Almost always does a radio check before they leave the unit. Typically they won't say much except "Manhasset, Radio Check?". Basically the most you'll normally hear over their radios is a unit name and the words radio check. They have phones throughout the building about every 30 - 50 feet or so, ALL of which can access the over head paging system.
As far as range, They don't typically do to well. I've heard from some of the staff that the radios will reach as far as Middlesex Hospital, But normally when they go on any off grounds type of function, They check out a cell phone from the main desk.
Not sure if this is exactly how they operate at this point, But it should give a pretty good idea of when to expect radio traffic.