I found a link which is quite interesting -written by a United pilot, who has taken the 787 course.
The Boeing 787, from a Pilot’s Perspective - View from the Wing
According to him the RAT supplies electricity as well as hydraulic power to flight controls (if needed).
P.S. The last 2 lines in his report read;
"
I think the 787 will be a great plane, but there could be some surprises with this level of innovation. Time will tell. "
How true - unfortunately!