I think I can reply to Suzy's questions.
First, the track is not as straight as suggested. If you pull up a map of the area, you can lay a straightedge across your screen from the point where the track enters your view to the point where it exits. You will see that there is an almost imperceptible jog in the track at the point south of the bridge, where the double track merges into single track and the Rayonier spur comes in from the west. I wondered whether this was just some kind of anomaly in the GPS, but I have talked with railroad operating personnel who have told me that the curve is there. So the approach track is not perfectly straight. Keep that in mind.
The bridge has generally been called a trestle, but this is not quite right. One characteristic of a trestle is the lack of a support structure above the deck. The relevant portion of this bridge was evidently built as a drawbridge. A steel truss structure, made of girders in a sort of lattice configuration, surrounds the track. Keep that in mind.
This train carried intermodal freight. If the train was 100% intermodal, its speed limit was 70 mph. If there were any other types of freight cars in the consist, its speed limit was 60. Not knowing details of the consist, we can surmise that the speed was probably somewhere in the range of 55 to 70 mph. Keep that in mind.
The film crew placed a bed or mattress on the track as a prop. At least one source says it was a gurney as used in hospitals or ambulances. The bed was on the bridge, between the film crew and their only "safe" and practical escape route. Keep that in mind.
Here's my theory:
When the train crew approached the bridge and saw it from a distance, they probably could not see all the way through the truss structure because the slight curve put them at an angle to it. Shadows might have also affected their view. They blew their horn for the nearby grade crossing, probably beginning less than 1/2 mile (30 seconds at 60 mph) from the bridge. Their first clear view through the bridge was when they went through the curve, only a few hundred yards from the point of impact, probably less than 15 seconds from the bridge. They would have initiated an emergency brake application at this point, far too late to avoid the collision.
The film crew scrambled to get clear, but their equipment, the bed, and possibly the bridge itself impeded their movements. The rest, you know. It's possible that this scenario may be incorrect on one or two minor points, but I am convinced this is the most likely sequence of events. We'll see what comes out in the investigation.
Why they thought nobody would ever notice their little prank is anybody's guess.
The other trains mentioned were Amtrak 98(20), which means train 98, the Silver Meteor, from Miami to New York, originating on the 20th of the month. and 52(20), the Auto Train, train 52 from Sanford FL to Lorton VA, originating on the 20th of the month.
