They're factory fitted
and for equipment servicing access as DTB suggests.
The plod roof has a couple of extra braces in it along with different headlining and the panels hence no sunroofs.
The rest of the car is a base spec with everything available as an option. Bare minimum for facelift UK cars was Xenon headlights.
Special was effectively the trim level rather than anything particularly fancy. Climate and electric front windows/electric heated mirrors were standard as they were on any facelift car.
Most were V6 3.0 or 3.2 but diesel was an option and the dash/body wiring reflected the civilian version according to engine. So the body harness included all the wiring from the sunroof to heated rear seats and rear quarter glass alarm sensors on the estate... which made retrofitting everything child's play.
Any plod cars with sunroofs were obtained from retail dealers once Russelheim stopped taking orders and a couple of forces had the foresight to bulk order and stockpile in early 2003 hence the spattering of 04/54/05 cars.
Forces that missed the Omega boat went straight to the BMW E39.