You could ask buyer to contribute. Try negotiating with Attorney that filed the lien they will often reduce the amount to get paid something.
Since it's traditional short sale, BofA will offer 1 year's worth of dues only. I have never had a traditional short sale file where they would not pay at least that.
I just had BofA pay $13,000 in dues on a $60,000 sale. 3 years of fees and dues. It wasn't easy but I kept pushing. It was a FNMA deal.
Much will depend on the State's laws related to HOA and how badly they want to do the short sale..