Are there any differences between preparing/cooking a turkey that was labeled "basted with real butter" vs a regular turkey?
Chances are most likely that it will be just fine. I suspect the brine process will "wash away" a lot of the butter stuff. I've worked in a meat shop before and the only concern I've ever heard expressed about them is dairy allergy, so do keep that in mind. Otherwise, I would (and have) just cook them as you are used to.