Interesting subject. I have a book here on the history of 5 Points. The book describes how there is no such thing as a "New York" accent - the so called accent is just the evolution (and variation)of a speaking and pronunciation style that came into vogue with the street denizens and early gangs that populated the Bowery circa late 1830's and 40's
The New York accent phenomena is residual from a manner of dress and behavior that we today might equate with "punk rockers" -
no need to analyze these things to the point of distraction. We have diseases to cure, energy sources to tap, space to conquer, Marxism to defeat....why do we need to nit pick on the verbiage of whether an accent is an accent or just the evolution of a speaking and pronunciation style....which sound to me all the world like what an accent is.