I did this in March with a CO E-Ticket in PHX. Stoodby at the NW counter, actually confirmed at the counter by the agent. They can go into your CO record very easily if you only have the ticket number with you. They can get it other ways, too, but that is the easiest.

I forget the name of the plan (I read about it here on FT), where NW will gladly take anyone else's ticket on day of departure as a standby, no charge. I have found that if asked nicely and from an agent that is not wet behind the ears (ie empowered) they will almost always try to accommodate.