I watched a video clip early this morning from the port authority starting from a couple minutes before the ship hit until just after the collapse. I zoomed in the second time I watched it and saw several vehicles sliding down into the river. I've crossed that bridge over a thousand times. The side railing is high and the angle of the cameras that monitor the bridge make it hard to see vehicles unless it's a semi.
In the clip below, you'll see the top half of semi's cross. What you can't see very well are private vehicles.
I don’t think so. The last moving cars were at 1:28 (two of them), and then traffic stopped. The cars that went into the water were stationary and likely the construction workers’ cars, sitting empty. That sadly does not mean the workers themselves survived, as they were probably out on the bridge itself.
There is a radio recording of a traffic officer reporting the ship coming toward the bridge perhaps a minute before it hit, telling someone to halt traffic. That’s why I think there were no moving cars at the time.