A little late to the party here - I was searching for railroad photos from Troy NY and came about this post.
That photo does show the B&M roundhouse in Troy. I lived on 8th St. as a kid. The roundhouse was at 8th and Middleburgh Streets. South of there was a freight yard which in your link has buildings scattered about it now. Rennsselaer St. had bridge over the yard that went from 8th to 6th. The B&M line continued south under Rt. 7/Hoosick St. There was no highway interchange or bridge over the Hudson River on Rt. 7 until the mid 70's. South of Hoosick St the B&M line went via a tunnel under Hoosick to Troy's Union Station which was located where the building now surrounded by 6th, Broadway, Union, and Fulton. NYC tracks continued south from the station. D&H tracks came to the station via the bridge shown in your link at Federal over the Hudson. When there were tracks here, this was an old girder type drawbridge (called the Green Island Bridge) with tracks and road shared. That bridge collapsed in a spring flood in the 70's and now you have the modern drawbridge with no tracks. You can see an angled building at the corner of Grand and 6th. Try to imagine the tracks coming from the bridge and curving south around this building. Also, draw a diagonal from 5th between Liberty and Washington down southwest to 1st between Ida and Canal. You can see how the buildings are irregular along this path. This was the NYC connection to Union Sta.
Unfortunately for me, I was born in 64. Union Station closed and was torn down around that time. The B&M was freight only into Troy. The D&H no longer crossed the Green Island Bridge. The NYC became the PennCentral and only operated freight in South Troy.
