Scott,
I love this song (I even recorded it once with my old VA7).
So, even if I am not a New Yorker, here is my opinion: I think that the Hudson river line refers to a Greyhound line which follows the Hudson river, to the upper part of the New York state (you know, towards Albany and the mountains: very scenic route, by the way...)
Just a poor european's opinion...
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Korg Kronos 61 and PA3X-Pro76, Roland G-70, BK7-m and Integra 7, Casio PX-5S, Fender Stratocaster with Fralin pickups, Fender Stratocaster with Kinman pickups, vintage Gibson SG standard.