E70 X5 Tailgate LED lights, what do they do?

[themule]

I have an 2011 LCI X5. I had an issue with a corroded fog light bulb holder in the tailgate, which I have replaced. There is also what seems to be a small LED light circuit board in there but they don't seem to do anything. Have looked on the internet and they seem either to be a brake force light or are in addition to the main turn signal / indicator - but that seems to be for US spec cars and I am not sure if it applies in the UK. Are they simply daytime running lights?
Does anyone know what these lights are meant to do and if they don't work is it a MOT fail?