MMO Champion (and a few of our tipsters -- thanks!) is reporting that the European WoW site has opened up registration for the Wrath of the Lich King beta. I wasn't able to sign in with my trial account (created for the Dingstravaganza a while back), but there's no question that the page is up (inside EU players' Account Management menu) and accepting signups. Of course, this still doesn't mean that anyone is playing the beta, only that signups are taking place. We're also being told that it's an open sign-up, so it could be a long time before these signups are actually allowed to play, especially if one of the beta keys from BlizzCon or WWI are used to run a closed beta first.
As for why this isn't happening on the main North American site yet, remember that one of the EU CMs was the one to break the news -- perhaps because WWI was local, they're starting things up early there (or maybe it's just a timezone thing, and the EU site has had more time today to get the signups going). No matter what, the wait is almost over -- there's no question now that we're closer to the Wrath of the Lich King beta than ever.
Update: Eyonix confirms the registration on US side is coming soon.