Steve-
Odds are it's two butts in one cryovac package. That's how I get them. The packages are usually 12-16lbs in weight, and one of the pieces is usually bigger than the other. If, for some reason, you have a picnic and a butt together, yes, they cook the same. If they are still attached, then it's a whole shoulder. You'll have to check it for fit on your grate (you can do this while it's still in the cryo---less messy that way.)
My money is on the fact that you have two butts in one package, though....
My 2?
Rich