COGCON is found on Wikipedia; the history of changes doesn't show it was changed right before this; and the source document #2, which is a .pdf deriving from President Bush's Executive Order, mentions COGCON2 as requiring essential personnel to be available at alternate sites on 4 hours' notice.

So the existence of COGCON looks legit; the question now (given the number of people claiming phone messages about it) is whether this particular heightening of the COGCON leve is legit, and whether the site you mentioned is accurate.