"Investigators are working to find out exactly what happened." Really?
My guess: they will conclude that the ship hit the bridge, removing two spans that were found across the bow of the bridge.
We all know that we don't know for a fact that the metal across the bow of the ship came from that bridge until the lawyers order some radiometric and isotopic analysis to determine if it in fact came front he same foundry as the metal the bridge was made from.
Next once the lawyers determine the metal was from the same foundry as the metal belonging to the missing bridge spans with a 99.76462% certainty, they will need to hire a team of experts to study the architectural plans to determine the weight and dimensions of the missing span, and then calculate for the effects decades of paint and rust would have had, and then then compare the findings against the piece of metal found on the ship. That will determine that the metal found is of the same size and overall dimension as the missing bridge span.
Now that the lawyers have determined that the span is of the same size, weight, and origin as the missing span they will next order a historical search for other bridges of the same size, age and origin along the waterway that the metal on the bow of the ship could have come from.
Once they determine that there are no other bridges of the same size, age or origin that the span could have come from they will file a motion with the court that they accept the fact that the metal wreckage found on the bow of the ship is in fact the missing bridge span.
Finally after acknowledging the bridge span was found on the bow of the ship, they will claim that the lights on bridge had faded from the proper color due to age, and on top of that, they were too dim and therefore do not meet COLREGS, so the bridge owner is actually at fault here.