Scripts & storyboards began about 14 years ago, but the project got sidelined by the success of Babe & Happy Feet and their sequels. Then later on, Mel Gibson got drunk, arrested, and went on a few tirades. Then the storms turned Australia into a lush green paradise.
Actual work began about 5 years ago, though. That's when we started seeing images of weird cars being built and shipped to Africa.
http://www.blastr.com/2010/08/1st_glimpse_at_killer_car.php