The Sadrists are using truck mounted rockets?

Within this story of a truck exploding killing 18 in Baghdad, we learn that the Sadrists are firing rockets on the Green Zone, in part, through truck launches.

Lt. Col. Steve Stover, a spokesman for U.S. forces in Baghdad, said Shiite militiamen were attempting to fire rockets at a U.S. base from the back of a parked truck about 800 yards away. But he said the rockets, which were supposed to be detonated by a fuse or timer, exploded early.

I don't think we've heard about that before.