Turbo failure in cold weather

My dealer has had 4 TDIs fail this winter. I am told it is a cold weather problem. The shaft on the turbo breaks. Of the four , Mine and another 2013 Passat had this happen. Fortunately it was under warranty but the cost was $8000. I was told the problem was taken care of by the remanufactured turbo.
Why doesn't VW have a recall on these ?.