The event itself, with this serving as mainevent, has been confirmed by MMAnytt.se. Gegard is one sneaky monkey, but I think (and hope) the mauler will emerge victorious.
Interesting match-up. Given that virtually all top 5 LHW's are booked, this is probably the best choice for Gus. And a great opportunity for Mousasi to shortcut his way to a #1 contender match come summer/fall 2013, should he win.
It is not inconceivable, however, that Rashad, Hendo or Machida would be moved to this card if injuries were to mess up their current matchups.