When Mike Ybarra stepped forward during Microsoft’s E3 press conference this year to showcase the newly announced backwards compatibility feature he needed a game to play in front of the crowd. He chose Mass Effect and the game has been available for Xbox One owners in the preview program for months now. However, the DLC for Mass Effect has remained off limits to Xbox One owners.
Until now. Gamers are reporting that they have been able to successfully install the Mass Effect DLC and play it on their Xbox One systems.
It does seem that the Bring Down the Sky and Pinnacle Station expansions will only appear if you have already purchased them. You could also try deleting the game and installing it again.