There used to be a logging mill south of Cloverdale at that spur. There was a private logging road (Kelly Road) that ran from Cloverdale to Annapolis (almost to the coast). With the construction of Lake Sonoma that spelled the end of the road

Asti Winery has a spur with 2 old Daylight cars. There is also a spur at the lumber mill that NWP is currently transloading in Windsor. They would like to get to Cloverdale to be able to load lumber right at the mill

There is a turn table in Healdsburg

The rock plant used to ship a lot by rail but their River Rock mining ended about the same time the NWP closed in the late 90's

That short spur near Shilo did hold a passenger car that was moved last week, see nwprr.net for some video of the move

NWP using the run around track in Windsor when moving the center beams from Standard Structures but that's as far north as they can go.

And yes SMART has finished all the track work to Airport BLVD.

Hope that answers a few of your questions