That may be true as such and if that applied to this case them fair enough but it looks all too fishy to me. Lights on just to go through a red light and get to the front of traffic then happily parade along.

I remember a few years back (probably the best example) in Barnet where I was waiting at the lights (passenger again) when a cop car pulled along side us, slowed down a bit put the blue lights on, went through the red light and promptly turned them off

I see what you mean though mate about another car being closer so they turn theirs off but in some cases like the one above, they use their blue lights for bloody convenience!!