I read several posts on the PC version that it does not stack and at the same time still reduces how much more XP bonus you get. I'd test it out and make sure before spending to much time on that character. Might just be a great weekend to start leveling an ALT that you didn't boost.
It doesn't turn off per the PC forums, you still loose the next # of XP and you don't get 3X XP. So you end up loosing portions of the double XP during the event basically. Just what I've read, use it was a warning and make sure. Like I said, might be ALT day.
Chances are the servers for the xbox one version are going to be down all weekend so it dont really matter does it. Unless there up and then i'll apologise for being a negative pooper.
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If you notice it doesn't I'd submit a ticket to get your Zen back