I've heard this is new thing for upcoming BMW.
Like few motorcycles, it will actually save alot of fuel
when the car is just stopped for few seconds.
( I dont remember exact number but around 60seconds I think)
This is all about fuel saving and reduction of using engine by some electrical thing while stopped if I remember correctly.
2006 E60 Gone!
2009 E89 Gone!
2014 F25 !!