Mass Effect was one of the very earliest backwards compatible games available to play on the Xbox One and now it looks like EA is going to be adding it to the EA Access vault.
It was first pointed out on r/xboxone, but we've since gone and had a little nose around ourselves and found the very same thing. On the "subscriptions" tab inside the game store on the console there's currently a banner for EA Access. And right between UFC 2 and FIFA 16 is Mass Effect.
That it's going to be added isn't a massive surprise, since EA has recently thrown the full collection into Origin Access, the compatriot service on the PC. It doesn't actually show up in the vault yet to download, but you'd not expect it to be too far away.