I'm writing this three years later, mostly because it needs to be written. Went for a ride on the Oswego Recreational Trail. I started at the official west end of the trail, but from the looks of it, it goes further to the west than that. It's in pretty good condition. All gravel, with only a little bit of mud. The trail is broken in half, at Interstate 81. The railroad and I81 never existed at the same time, so I81 never had any infrastructure for the railroad. The trail ends at the Central New York Chapter of the National Railway Historical Society just south of Central Square.
The trail continues on the east side of I81 south of Mud Settlement. There's a one-block section in Constantia which is now a field, but that's only because there's a road right next to the trail. The trail continues to Cleveland as a publicly owned trail. It continues beyond that as a privately owned trail open for recreational use to the public.