So the bird says it's a "Basted young turkey marinated with up to 9.5% of turkey broth, phosphate, sugar, and flavoring"
Methinks brining is unnecessary.
Yeah, it's basically already been done for you, but in a manner you didn't control.
If badger says he's had success brining even these types, he's worth listening to.

Personally for me, I've done it and it comes out too salty. Not sure about brining WITHOUT salt, since my understanding of the science is that it's the salt itself that causes the osmosis in solution, where equilibrium is reached and the protein absorbs the external salt/sugar/etc. from the brining solution.
But I'm no chemist. Maybe CD will chime in.
One thing I WILL add about brining, is that I've found I get better skin/color/crispiness if the bird is THOROUGHLY dried off and dried out before cooking. Which means, pulling it from the brine WAY before you plan to cook it--
like, 24 hours earlier. So what I do is pull the bird, rinse it off thoroughly in the sink, both inside and out (although with it spatchcocked there really is no "inside" anymore). After drying it off, set it on a rimmed baking dish or platter, open, in the refrigerator, and dry out for 24 hours before cooking. I've had great results with skin crispiness and color when doing this.