Apparently the coppers have an high success rate for catching speeders on that motorway, each time I use it I guarantee unmarked cars have pulled someone, nice clear road, hardly any traffic, easier to go a little faster .... easy pickings.
Having used the toll a number of times, I have never seen a marked police car on the road, although I have seen one parked just after the toll booths. There is however a green BMW 3 series that is a wolf in sheeps clothing and has a habit of being parked in the hard shoulder with its latest victim.
It is a great road and would be a lot of fun if it was closed, but never worth the risk from a prosecution or safety aspect.