Perhaps they have a similar reason to the one given here. In Taiwan Police have always got red and blue lights on, on their marked vehicles. The lights alternate red to blue and back but in a slower than strobe manner, they spend about half a second on each color. The lights are on the roof with at any one time red on one side and blue on the other.
I have asked a senior police official what their rational for this was - he replied that it was simply to make the police presence more conspicuous. If they want someone to pull over they make a short loud sound with their siren. In almost three years, I have never seen them chase anyone or use a continuous siren for any reason.
Ambulances and fire engines use their sirens and lights similar to the way Australian ones do.