You need to queue with the number of people required for the BG. so a raid of 15 for AB / EotS etc etc..
Are you sure about that? If thats the case, then there would never be any rated BGs for AV or Isle of Conquest, as you would have to have 40 dedicated people to do it. And that would mean that you could pick whichever Battleground you wanted as your "Rated" BG.

I was looking for some sort of blue post that elaborated on this, and I have yet to find one.

If this indeed IS true, that would be kind of f-ed up, and my excitement about rated BGs just went from 100 to 0.