It was Battle Angel. As the article explains he was working on his script for Battle Angel in 1999 before doing the show. Robert Rodriguez eventually took that script (because Cameron was busy with Avatar) and adapted it into the movie that was released, and used most of Cameron's designs. That's why it looks like a James Cameron designed world.
I actually have video somewhere on an old DV tape of my friend and I meeting Cameron at Disneyland in 2005 and my friend bugging him about when he'll make Battle Angel. It went like this:
Cameron: "Well I'm making a movie called Project 880 right now..."
Us: "You mean Avatar."
Cameron: "Yea, Avatar. Then Battle Angel will be after that."
He never made it. But Rodriguez's version was fine since it was based on Cameron's script and designs.