In my opinion, by attaching pads to the posts of wire rope barriers as a motorcycle & scooter safety measure the road authority accepts the wire rope barriers are so dangerous to riders that they have to modify the barriers to make them less dangerous.
Not sure what that says about liability.
The NSW Motorcycle Council commissioned a study a few years ago that reported that the posts in barrier systems were what did the damage to riders who hit the barrier. Wire rope barrier has the largest number of exposed posts of any type. Don't even think about the risk posed by the concrete and steel ends.