Mecanim - twisted model after .bvh import

I am new to mecanim animation system and I have problems with some armatures. There is a lot of free downloads of .bvh animations. Some of them work good, some not. For example a roundhouse kick. In blender, the pose looks just fine:

However, the default pose of the armature is weird. When I export this as .fbx and import it into Unity, the limbs of the character are strangely twisted:

What could cause this problem. Is it the bad T-pose? Or maybe the rotation angles of the bones? Is there a tool or function in blender to fix this?