usually mergers are in league with the other lines, I think the equipment aquirement would be the same, since this happened post steam, only diesels would be affected. N&W would have been looking for a better route into Chicago, NKP already had that, your pretty much looking at just a railroad name change. Best idea I can think of is that each of the operating lines retained their raIlroad names with one line being the owner of it. Again certain equipment would stay assigned to the railroad they were designed for but with diesels being more general purpose, they could roam easier.
If it happened in steam era, I doubt there would be much steam loco wanderings, but maybe N&W J's would make passenger runs all the way to Chicago and maybe even run on NKP and NKP passenger steam on the N&W etc. Berks would still stay on the NKP, the Y's on the N&W line.
I originally posted a question as to what you think the NKP loco roster would look like today if the NKP had indeed taken over the N&W Sou. and CR, and of course the W&LE would still have been in their possession. The topic was moved to the prototype forum, if you get a chance jump over read it and leave your opinion. What locos do you think they would or might have obtained. Mainline and switchers included. I originally posted it in the general discussion forum, because this forum gets approximately 15 times the viewers as the other forums, and I want as broad a spectrum of opinion as possible.
R. Staller