The comment about freight applies to all cases where passenger lines add track. It's track. It's there. Freight can use it. If passenger has an extra track, of course, it's normally not allowed to mix with freight on the other tracks. With competent dispatching, it won't hurt the passenger schedules ... too much. Same deal for the added track(one, perhaps two someday) between Sacramento and Roseville to allow more Capitol Corridor trains to go east of Sacramento.