AmtrakFan (John P.):
Regarding the CNO&TP that you mentioned, this railroad was acquired years ago by the Southern Railway System.
As of January, 2005, 74 NS diesel locomotives still carried the CNOT sublettering. I have not yet received the new updated list of NS units (to be issued in January, 2006).
None of these units were ever owned or operated by the CNO&TP when it was an independent railroad.
Southern just chose to "assign" these units with the CNOT sublettering.
All sublettering is either 2, 3 or 4 letters, with no more than 4 letters, hence CNOT for CNO&TP.
An increasing problem is that most of the NS sublettered locomotive units are units that were owned by the Southern Railway before the SR - NS merger, so they are getting up in age, and many have already been retired, are about to be retired, or will be retired during the next few years.
So, all of the "unique" sublettering created by the Southern Railway will most likely be gone within the next decade.
N&W was never thrilled with the idea of sublettering, so after the merger with the Southern, N&W did not subletter any units for their former acquisitions such as the Wabash, Nickel Plate, A&D or Virginian railroad lines. N&W just used NW sublettering for all of their locomotive units.
All new locomotives such as the Dash 9 and ES series units are simply sublettered with the generic NS. No use of subletters of acquired railroad lines whatsoever.
Except for PRRX, no use of subletters of former railroads that were absorbed into Conrail, either.
So, the practice of individualized railroad sublettering is no longer being practiced by NS. Too bad!
Hope that this is helpful.