Well, I think it was in Worlds & Monsters, but it might just have been the DMG (pretty sure it was W%M, though) there's a mention of "Who's really behind the Red Hand?"
Since the Red hand it mentioned, Elsir Vale must be part of the world as well.
By the same logic, all the characters and places of WotC's 3.0 Adventure Path (Sunless Citadel, Forge of Fury etc.) exist in the First Work setting as well. The way I see it, everything mentioned in Dungeon and Dragon that it not specifically for a named setting (FR fx) is for the PoL setting. And since there was a "Treasures of Ashardalon" article, Ashardalon and all that's connected to him must be part of the history of the First Work as well.
Or not?