Xbox One’s new backward compatibility feature has a couple problems. For example, it won’t be able to play Kinect games, nor will it be able to handle multi-disc games. However, it will be able to handle DLC, according to the official Xbox Support Twitter.
That being said, there is no guarantee that publishers will give the OK for DLC to work. According to the Xbox Support twitter, specific implementation will be left up to the publisher. In addition, it’s unclear as to whether or not you can purchase DLC directly from the Xbox Marketplace for your Xbox 360 games via your Xbox One.
We recently heard that the Xbox One backward compatibility feature is essentially all one digital game that runs as an emulator for Xbox 360 programs. There’s no particular reason why this couldn’t also make use of DLC, although there could certainly be some strange instances in which DLC could break the emulator.
Source: Twitter