I thought EA only had Porsche, but apparently this car as well.
The Pagani Huayra exclusive EA license was just until the end of 2011. Forza 4's January DLC pack includes it (and was released last night).
T10 once again showing how on the ball they are. Exclusive deal ends and instantly bam, there it is in Forza.
They obviously got it modelled and ready to go as soon as they legally could.
Kudos to the Turn 10 team!