The barge is pushed by the tug, as per the other thread and below, which is very manoeuvreable, so I'm not sure what is underneath that. I could always ask next time!
The whole thing is actually very carefully positioned and the tyres do a good job of protecting the paint. It is actually a very well organised set up, good equipment and very efficient. We usually load 1000 tons in round about 2.5 hours.