by mkm4
Sunnyside was never designed to transfer to GCT. It was only for Penn Station trains. Besides the documentation from the MTA (linked below), look at its position on a map. It was placed after the cutoff to GCT.
https://books.google.com/books?id=USs3A ... &q&f=false
https://books.google.com/books?id=USs3A ... &q&f=false