I have had a huge interest in the NE for the past 20 years, and spent a good amount of time in the early 1990's tracing the line.
To answer some of the questions here...
... west of the carbarn, the NE went into the hills, and while it paralleled the DL&W, it was a bit more of a roller coaster. The grade is pretty obvious.
... it did not use the DL&W tunnels
When I last "chased' the line, it was of course easy to find the route on the Scranton end in the street. Up the gap, you can still make out the little quarry and the grade plays tag with the highway in bits and pieces. From Clark's out to Dalton the line is pretty easy to follow. Don't lose it when you get to the high bridge site.
Dalton station was still there last I looked. Past the carbarn, the line went hill and ale as mentioned. I believe the Factoryville depot is still standing, much modified, and the grade there is EZ to trace, as it is all the way out to Nicholson. In Nicholson, one depot remains,a nd I think the DL&W fireght hous eis still there, which the NE served.
West of Nicholson the grade is apparent. I have never been to Montrose, so cannot comment.
JH