Xbox One backwards compatibility has certainly grown considerably since its launch in November and as part of that evolution they've released "Deus Ex: Human Revolution Director's Cut". While this might just be a regular title added into the collection, it's important to note that this is the first Xbox 360 backwards compatible title that was multi-disc. This was a feat previously said to be in-progress so it's exciting to see that they've actually managed to get it done. I was hesitant initially to post an article on it as they might have found a way around it though it runs just like on Xbox 360 and I've got an official statement from Xbox here.
From a Microsoft spokesperson:
"Yes, 'Deus Ex: Human Revolution Director's Cut' was the first multi-disc Backward Compatible title added to the program. We know fans were asking for this feature and our engineers worked hard developing a solution to enable it so we could further expand the titles included in Xbox One Backward Compatibility. We're continuing to listen to our fans on Xbox Feedback and work with our publishing partners to grow out library of Xbox One Backward Compatibility titles and will work to include more multi-disc games."
This is amazing as it means that more premium titles that required multiple discs such as those released later on in the generation will be possibly receiving support in the future. This includes things such as Mass Effect 2/3, Tom Clancy titles with HD packs and perhaps some games with bonus material including GOTY editions.
Update: Extra confirmation from Major Nelson via reddit with "I can confirm that the BC team has done work to support multi disc scenarios. Be sure to thank the BC engineers." Thread Here