@BT25 - Yep, that's how I think too. Especially if the light doesn't have a NEMA tag.
For city streets I base the light source of the light on the lights that surround it. An AE 113 surrounded by other M-250R2s that are HPS? Must be HPS. A Westinghouse OV-25 in a city that I know has mostly GE lights that are HPS and I've never seen it before? Must be MV (I've seen this a few times). Of course you should gather info on whether the lights are city-owned or utility owned, and whether or not they've retrofitted lights, and of course what lights they've bought and their light sources; this also applies to private property too.
For shopping centers/strip malls/malls, it's hard to tell, since unless you've seen the inside of the light and the catalog number, you can't tell if they're original or not. Private owners are also more likely to retrofit their lights, unlike city/government entities. Of course, if the light has a NEMA tag, then that makes your job of determining the light source easier.