Hi Martyn, you're a step ahead of me, I was going to post the same (already done on my blog).
This variant of the Genset is correct for the California Northern Shortline I model, although I've set it in the early 90's, with the release of this model, I can decide to swap to 'today' from time to time. All I need atlas to do is to release one for the CFNR, which they did for the earlier (and therefore incorrect) variant of the genset model.
Good news is also that they've done something about the 'waaay too chunky' handrails on the previous release.
By the way, here's the CFNR version in action. I am not too keen on the Rail America colours (Rail America owns the CFNR for several years already), I preferred the older green and cream colours)
CFNR 504 by
El Cobrador, on Flickr
And here a picture of a CFNR GP15-1 in the colours I would have preferred the Gensets to be.
CFNR 109 by
El Cobrador, on Flickr
Koos