I thought this article about street names and what they reveal about real estate prices might be of interest: http://www.nytimes.com/2015/01/25/opinion/sunday/the-secrets-of-street-names-and-home-values.html?ref=opinion&_r=0
I think it's pretty simple why housing is cheaper on numbered streets. Numbered streets tend to be closer to a city center, and while condos and apartments might be pretty pricey on 3rd st, for example, 25th st would not have such luck, being close to the center but too far out to be considered prime real estate.
When they say they didn't count large apartment buildings, does that mean they also excluded the value of individual units inside those buildings? Or that they did count individual units, but not the value of the entire building? I would think that not counting the vast majority of NYC properties would skew the data a lot more than including them!
But yeah, numbered streets are more likely to be in city centers, and more likely to be older areas.