Firstlly no one said he was full of sh1t, He raised a few valid points.
Many police own nice cars, but they belong to the officer.
Yes its true they are always on duty to a degree, yes they can fine you when out of uniform and off duty while driving their own car.
We used to have a regular user of SAU that was an officer and owned a very nice R33 GTR with a number of mods. Was a very quick little car in fact, but he owned it.
Many used to bug him to ask questions about "what should i do if" and "is this legal" and so forth.
The traffic branch have many types of D cars, but all are less than 3 years old and must be current models, this is their own rules.
Remember when they retired the Monaro's which at the time were only about a year old. This was due to Holden ceasing production of the car, so they switched to XR6 Fords F6 Typhoons for the highway patrol. As they were and still are current.
They DO NOT however drive conferscated cars that belong to members of the public, under any circumstances on a patrol.
PS> Sidenote, you should also have a search in the QLD section for a topic called "Undercover cop car register" as it is a thread that posts many a car that has pulled someone over.
Its an interesting read actually and its a pity it does not get used these days.