Hasn't it not actually been ICQ for a while now? I thought the original service with the numbers (387175) was shut down and replaced with something else entirely at some point.
i was able to sign in with my number and password just now, had to click link in the upper left to get around the phone number request
I believe you're right on this. The original ICQ number accounts got merged into AOL Instant Messenger, and for a while you could log into AIM with your ICQ number. I think the original ICQ died when AIM got shut down.