Unmarked one arent actually speed cameras, they're info gathering vans, used to decide wether that road will become a speed trap road in the future.
well i saw a unmark red van yesterday on the malahide road near the applegreen petrol station. it wasnt a garda van as the camara was up on the roof and it couldnt of being a info gathering van as that part of the road is on the garda safety camera's website.