I think it's pretty obvious from Pulis' comments that we are prepared to sell Fazio to West Brom without Berahino as part of the deal. This tells me that it is more important to get rid of Fazio, a player we bought for a considerable amount last summer, than to get a player that the manager wants.
Actual swap deals don't really happen - mainly for accounting reasons i would imagine. So any 'deal' in place would involve one player moving before the other.
Now if you think we'd sell Fazio at a loss after only a season to a club we have been in discussions with about one of their players without it being a precursor to that deal being done then that's fair enough - personally the Fazio to WBA transfer all but confirms Berahino is on his way here (imo)