They look like a set of barriers that coaches, buses and lorries pass though as they are extra wide. As you say probably there for no other reason than to stop cars dropping off on the road to avoid payment. On that same plan I have noticed a second floor link bridge between the two multi stories towards the south side. It seems wide enough for traffic.
Mini traffic lights have been installed into each bus bay in the bus station area, this is to help control bus movements and indicate when it was safe for buses to reverse from parking bays. They have yet to be switched on.