Bernie at Orphan Road found an interesting article from Spokane. Seems as if the local government is looking to preserve right of way through zoning. Is there a way to preserve ROW that isn't a taking but doesn't cost the city money? I would have thought this qualified as an easement where the city can push for the land owners to allow the city to use the property for a specific use such as ROW, but the city has to get permission from the land owner.
In Portland, the Lake Oswego rapid streetcar would run on an existing easement that allows the rail line to run. If the current shoreline trolley stops operating, the easement reverts to the original landowners. This was discussed in recent comments at Portland Transport.