Infinity Ward's Robert Bowling has said Raven Software's part in the Call of Duty franchise was to help Treyarch with DLC as well as "random user interface and engineering tasks," and it will be helping IW out with Modern Warfare 3 "in the same capacity".
"The same can be said about bringing in Sledgehammer Games," said Bowling to GameZines, stating the firm comes from "a very different background and who have added a lot to things like the storytelling and the way that we do things that have been beneficial.
"It's co-development across the board as if we were one team. We're all checking into the same tree and we're all building off the same builds, so there's never been a clear divide of 'this is yours, this is ours, don't touch this, don't touch that'. It's across the board of playing to each others strengths and weaknesses."
Modern Warfare 3 is out on November 8.