I think you have to play on the Nuketown game mode.
no, i have been playing ground war all day and keep getting my double xp, 2 more levels for prestige 10
I downloaded update today and now I'm not getting double XP
Double xp is for medals that are awarded, e.g. - revenge, double kill, bloodthirsty etc, they will flash up during game showing x2 XP and match bonus for finishing game xp