So more than a month ago I applied for IDXbox and I decided to share my experience for you to get a better idea of the program.
First of all you have to apply here:
After around 2 or 3 days they will contact you and give you information about the process and send you an NDA to sign (to protect your ideas and theirs).
After signing the NDA then they will send you a form to complete which is about the concept of your game, it's a really long form that asks everything about your game.
After completing the form, you have to wait for them to review it (they says it takes 13 business days but mine took around a week)
Then they will email you about your concept approval (if they approve your game concept) and tell you to wait around 15 business days to complete few agreements which let your to release you game for Xbox One and Windows 10 and get access to Xbox Live documentations.
It is really simple and they are really supportive. I hope we see a lot of Construct 2 games on Xbox One soon.
if you have any questions feel free to ask