I bought The Saboteur from Amazon a while back when they had it on sale for like $7 or something and I had to start the download with Amazon. Once I did that, I think a key appeared in my Amazon account and taking that key, I stopped the silly Amazon d/l and applied the key to EA DM.
Like magic, it appeared. I say this, but I also warn you that there are some games that are supposed to be usable on EA DM (and to be fair work for others) but don't work for me. Mass Effect will not register on EA DM despite the fact that it does for others. Nor will Mercenaries 2: World on Fire, which also works for others.
I can't get those keys to work at all. That said, I got games like Red Alert 3, Mirror Image and The Saboteur to work when SOME others can't get those to work from what I gather. EA DM is unfortunately a crap shoot on which games it'll take. I actually like EA DM, for the most part, because it feels like such an extra to me. I'm not required to use it, I can use it to get free re-downloads for games I already bought on disc (or elsewhere), it's free, the downloads do NOT have the silly 1 year limit EA used to impose, and the EA DM software's not bad as long as you don't let it start up with Windows. I wish they'd add an option to disable the chat function from showing up on the screen even after being disabled, though.
Anyways, hope that helps.