The present CSX Chicago Line from East Syracuse to Belle Isle was originally the West Shore main around Syracuse. The bridge abutments date to about 1883, and the NYC bridge numbers are based on Weehawken mileage. Sometime prior to 1898, based on viewing a topo map of the time, the NYC had already built the first yard at East Syracuse, and they had appropriated the "Lake Line," as the NYC called it, from the west end of the yard to SS-2, west of Syracuse. The West Shore appears to have had a branch into downtown Syracuse from the east which joined the NYC main east of the passenger station. The Chenango Branch connected to that line west of Dewitt Yard. By then, a westward train from Utica on the West Shore did not have a direct route into Dewitt Yard without reversing, nor could it head up the Lake Line without backing into Dewitt.
Until the NYC main through downtown Syracuse was abandoned, the connection to the Lake Line on the east was via Dewitt Yard tracks, and ca. 1959 there was no main track east of GS Tower at Clark Street. The Lake Line main tracks ran from GS to Tower 2.
Larry - It seems that my info corresponds with yours.