Personally, I think you should show the finished CAD for checking, especially with locomotives or anything with lots of curves. Given the cost of tooling I just think it makes sense to check you haven't made any howlers. While I take Justin's point about internet experts etc. and companies doing their own research, capturing the shape of something like a Deltic is really quite difficult, especially if the CAD operator isn't a railway enthusiast. Laser scanning isn't the be all and end all either as the face of the DJM 71 shows.
The best way to illustrate this is that although I haven't ordered my Deltics yet, I definitely will at some point. However, I'd be sticking with the Bachmann model if you had produced them based on the print you showed at Warley...