If you want a little fun, there are free Microsoft Train Simulator (also work with Open Rails) routes for the NWP Willits north (EUKA era) and Cal Western (also approximately EUKA era, but somewhat generic). Both are fairly realistic, within the limits of the software, but may include (especially in the NWP route) a few imaginary traffic generators to make the model railroad runners happy with potential switching.

Real NWP ran a lot of lumber out of the North Coast, but that was in the days of smaller cars, no environmental laws, and economically viable small loggers in every other gulch.

When I lived in Santa Rosa (1970s-80s), there seemed to be more gravel trains (many out of Healdsburg) and general freight (usually with some lumber) than real "unit" lumber trains - maybe 1-2 real lumber train(s) came through on days when I could observe them. At that point on the line, only gravel trains and occasional locals seemed to run in the daytime; everything else was at night. And this was when there was still regular wood products traffic originating from the North Coast, Willits itself, Cal Western, the Ukiah area, and even a bit from Cloverdale. So I have to presume that some major shrinkage in lumber mills happened before that, with the final blow falling after EUKA closed up. Have to agree that under current conditions there's really not much potential for lumber by rail - what's left in the way of mills is well-covered by trucking - and certainly not enough to justify rebuilding the line through the canyon. Even Willits or Ukiah may be a stretch, but I'll never say never. Forever is a long time ...