From the pictures on wgrz.com it appears the train was headed south. Fair use quote from the article:
"Buffalo Police spokesperson Lt. Jeff Rinaldo says they are still investigating the cause of the accident, but it appears a portion of the cargo train was too high for the bridge. They're still not sure if the stacked freight cars were too high from the start, or if the train's load shifted at some point during the train's movement."
According to a not-so-recent timetable 20' 2" is the height limit on track 1, and 19'10" on track 2. If the load was too high, you would think that it would have hit another bridge somewhere else along the way.