Rails around Hum.Bay may have been worn out before NWP stopped running. Except for rust, they haven't worn out just sitting there. That said, some may in fact need replacement.

1) They probably ARE old, and a track inspector would most likely condemn some of them. In the later years of SP-NWP, and almost certainly during the years of the cash-strapped successors, track maintenance was minimal (at least from what I saw when living in the Santa Rosa area in the 1970s and 80s), then of course everything has just sat there for 10+ years. While there will be more problems with ties and roadbed, some broken or otherwise damaged rails are almost a certainty.

2) Given age etc., it's very unlikely that the track would work for modern 286K# cars even if all the rails were fine. If they're planning on unrestricted operation even at moderate speeds (say, 25 mph or so), some upgrades will be necessary. Look at what was done recently on the south end, and factor in double or triple the rainfall plus a few earthquakes during a longer time out of service.

Frankly, given the environment and the amount of time out of service, I'd be more worried about condition of the bridges and culverts. That'll cost more to fix than any likely rail issues.