put the prius on the M1 at 85, then lets see how economical it is.
Fact still remains it has a massive carbon offset used to build the damn things, its much more environmentally friendly to build normal cars.
Hybrid drive is not the way to go.
Your example highlights the very scenario where a hybrid car is operating exactly as a conventional car with a bootload of redundant batteries and electric motors though. It's hardly likely to be a glowing endorsement for Hybrid cars.

One of the two times I have been in a prius was in a taxi travelling through the centre of Milan. Read: Italian driver, Italian traffic, Italian Traffic light sequencing.

The average MPG was reading (metric equivalent of) about 55 MPG IIRC, and the reading was stable. The way this guy was driving, I can tell you that if he had been in my 3.2 Auto (or any petrol Omega) he would have been doing low teens MPG.
Hybrid cars have a place, and solve a particular set of problems associated with a particular type of driving. Personally, I wouldn't buy one because I rarely do any urban driving and I'd want to know what the longer term costs of ownership are.
If I drive through the centre of Milan every day I sure as hell would ditch the Omega though.
Kevin