The adjustable rear wing returns to its high-downforce state as soon as the driver presses his brakes. So that should clear up any confusion regarding what it does during an overtaking manoeuvre.
It activates when the car's within one second and deactivates when the driver presses the brakes.
At the meeting of the FIA World Motor Sport Council in Geneva in June 2010, an adjustable rear wing system was confirmed as an addition to the 2011 rules.[2] It will be introduced to aid overtaking, serving as a substitute for the F-duct system. In a similar system to the KERS regulator used in 2009, the adjustable rear wing would only be available under certain conditions; namely, drivers will only be able to use it when they are within one second of the car in front, but it would not be usable within the first two laps of a race except in the case of an early safety car. The system is expected to offer drivers an additional 15 km/h (9.3 mph) when passing,[69] and will deactivate when the driver first touches the brakes after using the rear wing. The concept, which has been negatively received by drivers and fans alike,[70] could be dropped if it proves impractical or unmanageable.[71]
The sources are there, Autosport. But they're old so you need to subscribe.
http://en.wikipedia.org/wiki/2011_Formu ... al_changes
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Also I remember reading that reduces the angle of attack (and thus drag) by lifting the wing up instead of pulling it down, thus if the mechanism does fail it defaults to the high drag setting which is much safer.