Supermax does share some similarities with the Green Arrow script in that it's about a maximum security prison that's stocked full with unnatural individuals. Instead of DC villains, this one is full of the supernatural. The story centers around a skilled prison guard who is reassigned to the creepy facility just in time for a prison riot to break out. He's forced to team up with one of the prison's most horrifying inmates to survive, and fight his way out. Who or what that inmate is remains a mystery. (Fangoria has an interview with Nelson and Rouse up and while they don't reveal much beyond their enthusiasm, you might find it a fun read.
Bloody Disgusting first broke the news that Supermax had been sold to Columbia, and now The Hollywood Reporter has confirmed that Rouse and Nelson will be seeing their nightmares come alive there. Production is set to begin in early 2010, and while many have predicted this Supermax will kill the DC one, I imagine that the issue will be fixed by one or both films changing their titles.