[Rigorous]

Originally Posted by ckramme <snip> Not all realms are connected together, several are connected in Battlegroups. These are EU battlegroups - http://eu.battle.net/wow/en/forum/topic/859138430

for EU realms, that appears to be outdated information according to:
http://eu.battle.net/wow/en/blog/943559#blog as there was also an EU regional battlegroup merger.

strangely, I can't find anything delineating the US region-wide battlegroup merger that occurred back in November(?), as it seems all of the "official" information about that change was on the "old" (www.worldofwarcraft.com) site....all I can find are fan sites discussing the change...like this. However, the current lack of "Battlegroup" forums on the official site would be a good indicator, I think.