There probably isn't one that's been published, but it would be easy to lay one out for yourself. Bachmann has announced an N scale 44-tonner, so you'll even have the perfect motive power available soon.
If you do plan to do your own track plan version, I'd suggest that you open things up a bit to allow longer runarounds and sidings and a bit of staging, if you can. The G version is very, very tight and a little more relative length in these areas will make the layout much more fun in the long run.
Byron
Model RR Blog