All of these have hits on google when you search for `"Upstate starts at" street'.
(I have no idea what the person who said 105th is talking about. I could imagine someone saying 110th, since it's "Central Park North". I figure 105th is a typo.)
I was thinking of the quote "The Midlands start at Tottenham Court Road", from the movie Kinky Boots, and realized I'd heard something parallel said about Manhattan. For people who know London or New York, these are basically equivalent hyperbolic statements. One may even have inspired the other.