^ That is not impossible, I just don't think it is likely.
For one of those cars to be moved (or moving as the article states) there would have to of been power to move the car off of the chain system and into a free moving state.
Now it is possible that one of the cars was at the MCBR (I don't remember if PW has one, but I assume there is), but even then, in a powered down state, the brakes in in a "closed" state.
I would like to have more detailed information, but I doubt any will be released.