Once you've done that, you simply sign in to your profile on the Xbox One where you'll find the Xbox One version available to download as well at no extra cost.
Considering the Xbox One disc copy is still going for £46.14 and the 360 disc copy for £21.40, this is very much a steal if you haven't tried it yet. Plus double the achievements and you can play with your friends on either platform at a press of a button!
I took opportunity of an offer on this awhile ago having not played a Call of Duty in quite sometime and thoroughly enjoyed it. You can check out my previous review on it and the Extinction Mode (which is worth the asking price alone as it's a helluva lot of fun!) here http://www.backwardscompatible.co.uk/call-of-duty-ghosts.html
So that's Call of Duty: Ghosts Xbox 360 and Xbox One Digital Combo for £27.44 with FREE shipping in the UK with orders over £10.
UPDATE: Now £26.92!
Add it to your basket here http://www.amazon.co.uk/Call-Duty-Ghosts-Digital-Combo/dp/B00FZFL76G/ref=sr_1_1?s=videogames&ie=UTF8&qid=1394044361&sr=1-1&keywords=ghosts+combo
Source and thanks to http://www.postabargain.co.uk/
You can also enjoy some gameplay footage I uploaded of Extinction using Upload, Upload Studio and OneDrive below.