Unfortunately, the car pool lane is not all wine and roses--there are some unwritten rules. In california, people seem to believe that the carpool lane has an unlimited speed limit. So if traffic is moving along at 75 or 80 in the regular lanes, then the cars in the carpool lanes have to be going faster than that. That's a problem when trying to drive the ActiveE efficiently--anything over 70 is not efficient.
Also, people seem to think you can enter or exit the carpool lane whenever you like. However, crossing the double yellow line to get into or out of the carpool lane prematurely is a moving violation--complete with points on your license. As opposed to driving in the carpool lane with only one occupant (for cars without our lovely white stickers), which is a civil fine but not a moving violation so no points.
The point is, you have to choose wisely. It is great to be able to enter carpool land, but not so great to be pushed down the freeway by an impatient driver while trying to maintain an efficient speed. But on days when the regular lanes are stopped, or nearly stopped, then its clear sailing in the carpool lane.