You are correct. New York State Police is also licensed to 155.475. More info can be found in the FCC database. I'm not too familiar on how the NY State Police frequencies are catagorized, however the FCC database does indeed list this frequency as "active".
155.4750 is the national police frequency every department in the country has it no matter what other radio system they're on! The usualy thing is I hear NYPD on it fairly regularly and they don't seem to be talking to other angecies, it actually gets kind of annoying