Does a creature have cover when moving through an ally space?

Suppose in the following position A has a reach weapon (and is an enemy of both B and C, not sure if that changes anything). C has soft cover from A, but is also out of reach. Now, C moves closer to A – through B’s square then into the empty square. Movement into the empty square would normally provoke an attack of opportunity for moving out of the square threatened via reach, but if B provides soft cover for those moving through his space, that attack cannot be taken. So. Do any rules, FAQs, etc. rule either way?