I have successfully transferred my European (German) code to a chap in the UK. He was able to redeem and download both the game and the Day One Launch pack. While it does not give any insight to code trading across PAL/NTSC territories, it provides some insight.
While writing out a more detailed description of the behavior, I stumbled upon the solution myself.
When you try to install the game over the internet, just let it start, and then cancel it. This will both remove the installation and download from the queue, but apparently also remove the knowledge of the installation from the Xbox One.
So:
- Start the online install
- Cancel it
- Return to the home screen
- Notice that the disc tile has now changed to "Install disc"
- Activate the disc tile to start the installation from the disc.
This worked, the game now installs from the disc. Obviously any downloaded DLC's will still need to be downloaded, but for the purpose of this question this is not relevant.
Now, what do you do when you get back home and want to plug in the external drive?
Here's what I did. I first uninstalled the game using the storage management.
This makes my Xbox One forget that I had the game installed. Make sure you don't delete any savegames you have on the console.
Then, you turn off the Xbox One, plug in the external drive, and turn it back on.
Once you do that, the disc tile still says "Install disc". Ignore that. Instead either use your pinned link to the game, the tile for the game (if it shows up on the home screen), or navigate to your games and apps list and activate it. You should get a message saying not to unplug the external drive, and that your game will be ready soon.
A few seconds later you can try again and the game should now start.
Best Answer
Similar to the My Games & Apps menu that shows you all content installed on your XB1, you can see what content you have installed (and ready to install) on a per-game basis.
To do this, press Start on your backwards-compatible game's tile (on the Home screen or in your game library), and click Manage.
This should show a screen similar to your games library, but the "Installed" and "Ready to Install" should just be for your game. Any DLC you own should be in the Ready To Install category, as in the screenshot below.