[:(]did they ever figure out what caused the bridge to fall and did train traffic resume
They have not determined the cause, and it will likely take months if not years to do so. They plan to recover all the steel and roughly re-assemble it in a field. The law firm Schwebel Goetz & Sieben has asked a federal court to grant its experts immediate access to the Interstate 35W bridge collapse site so they can begin their own investigation that could form a basis for wrongful death or personal injury lawsuits. They said that the findings of the NTSB are not admissible in court, and once the wreckage is removed from the river much valuable evidence will be destroyed. A judge has turned down their request.
Considering the complexity of the collapse, number of deferred maintenance items, the possible effect on the collapse of the on-going bridge re-decking project, and the potential conflicts of interest in the search for a cause, I will be amazed if the cause of the collapse is ever specifically determined to the satisfaction of most people.
As far as the rail line affected by the collapse is concerned, it was just a dead-end spur anyway- no “rail traffic” to speak of, just some parked covered hoppers.