Inwood should be a good spot for scanning, and you should hear alot more besides the LIRR, especially if you're near the water. Amtrak, the subway, Metro-North, not to mention the freight roads in NJ, if you have a decent antenna. Good luck with the scanning...
Also, the train was reporting that his speed control gear (ASC) was tested. Some roads have this or a variation of this (Amtrak calls it "ACES" or ASCES), but some do not, such as the subway. Poke around in the archives of each forum (LIRR, Amtrak, etc.) and you may find answers to your questions...