There really isn't a schedule for freight trains. They run when they run. They tend to run around the same times each day (ie NS 212 is through Phillipsburg, NJ in the early-mid morning), unless something causes a delay.
Not only is there not a set schedule, but for some reason I am thinking that schedules are not published for security purposes...I might be wrong, but i think I remember my RR'er talking about that a few months back.