Last year's Supreme Court decision was for a completely different situation and would not apply to the NWP's line north of Willits. In that case, the Forest Service tried to establish a trail on land it had exchanged with a private citizen; the exchange included an easement for an existing railroad, but the line was formally abandoned years ago. The patent granted to the citizen provided that the easement would vanish five years after abandonment, and the Supreme Court agreed.
This article summarizes that case pretty well.