When a game becomes backwards compatible, everything from DLC to exclusives become available on next gen. However, one cannot install an exclusive content on next gen if they did not have it on 360. But oddly, Microsoft seems to have neglected to make the “UA/Counter-Assault [W]” chestpiece (a GameStop pre-order exclusive) from being available on next gen to those who previously had it. It’s not in the store, it’s not installable. If I apply it to my Spartan on 360, it’s gone on the Xbox One.