A short sale is most of the time not even covering all of the owner's closing costs. First you need to know if the sale of the home has lender approval. The only reason someone would be selling their home as a short sale is the home payoff is more than the owner can get for selling the home. The lenders will only take so much of a hicky on the sale...will they pay pay buyer closing costs...it is all nego. but remember they are already upside down with the sellers fees.
They, who? Actually, it doesn't matter. In real estate transactions, everything is negotiable. However, the lender who is taking the loss may mandate that the mortgagor (homeowner/seller) pay for certain items or participate in the loss in some way. Every deal seems to be different in my experience.