What happened to the Havok engine Physics that were going to be added to the World of Tanks PC?

I'm still curious, whatever happened to the Havok engine physics that were going to be added to World of Tanks.  Why the long delay in adding it?

Also, why did Wargaming choose Havok engine physics when the BigWorld game engine that is used by Wargmaing for World of Tanks and other games naively supports another one of the other game physics software programs, PhysX?