I see this word everywhere as applied to new and mostly new diesels. But it baffles me. It makes no sense. I thought all diesel cabs extended out to the edge of the frame, and thus all are pretty much the same width. Is there such a thing as a "narrow-cab" diesel? Haven't seen mention of one. I suppose what everybody really wants to say is "wide nose," but nobody says it.
Actually, some people do say "wide nose". And you're right, that's what they all mean.
I can think of some truly "narrow cab" diesels, though.
Most Vossloh G2000s are "dogbone" configuration:
http://www.railpictures.net/viewphoto.php?id=182172
http://www.train-photos.com/picture/number4504.asp
But some look like... well, this:
http://www.fotocommunity.de/pc/pc/chann ... y/15706546
http://www.railpictures.net/viewphoto.php?id=63025
There are also a couple US industrial switchers that have been modified with a cab like that. Can't remember where I saw the pictures.