Back at Gamescom earlier this month, Phil Spencer, Microsoft's head of Xbox, announced that Xbox One would soon support the pre-purchasing and pre-downloading of games, starting in September with FIFA 15 and Forza Horizon 2. It appears, however, that we're getting such functionality sooner with Madden NFL 15.
As several users have pointed out, you are now able to pre-purchase Madden NFL 15 for Xbox One via the Xbox Games Store. Though the game doesn't release until August 26, the product page points out that you may download the game from Xbox LIVE before then; however, it will not be playable until 12:01am on release day. That is, unless you happen to be an EA Access member. If that's the case, then you can not only download the game, but you can begin playing the six-hour trial and have all of your progress carry over once the full game releases. Additionally, EA Access members get 10% off their digital purchase.
Though the Xbox Store specifically lists the EA Access version, some users have stated that they are still able to pre-purchase and pre-download the game even without having an EA Access membership, suggesting that this is Microsoft's doing. To that, head of Xbox Phil Spencer responded that Microsoft "will be announcing the future pre-order/pre-download dates and games soon."