According to the date base the CSXT Berkshire Sub goes from MP92 in Wilbrahm MA to MP 192 in Post Road NY. Where about's is Post RD? The only one I could find was in the Bronx.
CSX Berkshire Division vs. AMTRAK Post Road Branch
Post Road MP:192 (Actually MP:191.8) is adjacent to the physical Old Post Road in the Town of Schodack New York State section of the CSX A/K/A CIA RR "Berkshire Subdivision", the Post Road you may be referring to in "Da Bronix" does exist but is somewhat East of the MTA Northern Division (Metro North) tracks just South of the NYC/Westchester county Line in Yonkers.
According to the date base the CSXT Berkshire Sub goes from MP92 in Wilbrahm MA to MP 192 in Post Road NY. Where about's is Post RD? The only one I could find was in the Bronx.
There might be some useful information in the RR Wiki articles that are in the Category:CSX Transportation. This category is subdivided into the related states.
The Post Road line (branch?) goes from the CSX main line to the boundary of the Albany-Rensselaer Yard, where the Amtrak station is located, and is under the control of Amtrak.
The Wikipedia article is a little outdated. The Post Road Branch connects to CSX at only one end now. The Hudson River Line belongs to Amtrak. (CSX does run freight on that line, but Amtrak controls the track.)
To clarify, Hudson River Line is Amtrak from Schenectady to Poughkeepsie, where it becomes Metro North track.