IIRC, there was a push a few years ago to get the rangers certified as law enforcement and armed, but I don't think it ever materialized. Historically, I think OSP cadets were used for patrols during peak seasons or in busy areas.
Same here -- any vehicles I've seen have a VHF antenna (if they even have one at all). They were running a couple of frequencies in the 159 MHz area, but that was probably simplex in the local park(s). It sure would make a lot of sense to give them access to ODF's repeaters, though, especially since they are working in many of the similar areas and terrain...