I have moved down to Elmira, so it's easy for me to go exploring here now. Here is what I know about the EC&W (the trolley):
I know of no trace between Big Flats and Corning, but there is a bridge at the intersection of Main Street and NY-352 in Big Flats.
My understanding is that the power line east of River Street is built on the ROW, and switches to the west of NY-352 when the power line does.
As NY-352 turns to the west, the trolley crosses the highway and then crosses Sing Sing Creek on a bridge with concrete approaches and a missing steel trestle.
It visibly stays on the other side of Sing Sing Creek and crosses NY-352 again when the creek does.
It follows Sing Sing Creek then becomes Maricle Lane (a private driveway) until it turns 90 north.
Goes through the woods (you can see it in the vegetation that grows on it), cuts behind the houses on Palisades Blvd,
then becomes Cottage Drive East, crosses NY-352 and immediately goes over a concrete arch bridge over Old Narrows Road.
I expect that Old Narrows Road was the trolley-era routing of NY-352.
It's then clearly visible on the north side of NY-352 to the intersection with NY-225, where it fades out.
About halfway to NY-225 is a creek on the north side of the highway and another concrete arch trolley bridge.
Entirely street-running through Elmira. Maybe there are rails in some streets? Certainly some streets still have bricks under them.
We next pick up the trolley running alongside the Erie on the way to Waverly.
At the southern border of Southport is a farm road and private crossing. A few feet north of that is a defunct creek.
The Erie filled in the creek bed, but the trolley bridges (two of them) still cross a creek bed, as does NY-427, Maple Ave.
The southern abutment of the bridge at Seeley Creek is still in place but the northern has been destroyed.
The trolley railbed is quite visible next to the Erie's tracks.
Just south of Dug Road is the trolley's powerhouse. You can see the portals for the power lines on the back wall. It's now the town museum.
Not sure if the trolley follows the Erie or the highway between here and Wellsburg, but on the north side of the Erie's bridge over Bentley Creek are trolley bridge abutments.
I know of no traces east of Wellsburg. Happy to be filled in.