I know that the N&W was a latecommer to diesels, so they they never really had E and F units the 60's. In most of the F-unit pictures they were in places like NY,NJ, and PA, so why were they there, but at least one was in wreck so that kind of explains some things. I have noticed leased E-units, but did the N&W use there E7's just in former Wabash territory?
In the late 1950's the N&W often leased ACL E-units (in purple & silver) for their passenger trains. There are/were quite a few photos extant from various locations on the old lines of the N&W showing this practise. In 1964 when the N&W variously leased/bought the Wabash, Nickel Plate, AC&Y, etc., only the Wabash had any amount of E and F units and from photos of that period (available to me) it appears that these units seemed to stay in their accustomed Wabash haunts. Perhaps someone knowledgeable about those fallen flags could give you more information.
I think it would have been neat for the N&W to have acquired a PA from the NKP, and also it would have been cool for the N&W to hve used F's on mine runs, but I don't think they did. I do admit the leasers did look nice on passenger trains.
RF&P as well: http://www.railpictures.net/viewphoto.php?id=294503&nseq=9 N&W ex-Wabash F7s appear to have been frequently leased to CNJ: Leased N&W F-7 on Jersey Central NW CNJ RDG Bethlehem, PA 1968
One of which was acquired by the Wabash to rebuild one of their PAs... which N&W put an end to right after the merger.
