I have listed and sold 5 short sales so far. The ONLY way to know what the bank will accept is after a contract is sent to them and they come back and say "we need no lower than X dollars" to get this approved.
Then the listing agent knows exactly what the bank wants and lists it at that price. However if they don,t put in the listing (usually for agent information) that it's an approved short sale for X dollars there's no way to know and compile a list of "pre-approved" short sales. Also no way to know what the bank will approve until they get a contract and order the BPO , which is another way to refer to a market analysis. Be aware that short sales don't usually sell for a bargain price, they sell for current fair market value....which just happens to be less than what the seller owes to them.
EG: seller owes $200,000 ,BPO says current fair market value is $150,000. Bank has to agree to take the SHORTage of $50,000. If they get a contract for $$100,000 it's most likely they will reject that offer and tell the listing agent they will not take less than $150,000. that's what I consider a pre-approved short sale.