I pursued 3 types of companies to start listing REOs.
#1 BPO companies.
BPO companies only assign BPOs to Realtors, then they submit your completed report(s) to the investor/bank/lending institution that ordered it. I've completed a lot of BPOs for SummitValuations but they will never send me (or anyone else) an REO listing. They will, however, will pass my name along to their client(s) that order BPOs. So if you do consistently good work for BPO companies they forward your name on to the companies that actaully need to assign their REO listings.
#2 REO Companies.
REO companies companies are next. National Default Servicing LLC (NDS) is one that I have done a lot of work for. NDS orders their BPOs through SummitValuations and they assign REO listings to agents that complete BPO work for them and are located near the REO property.
#3 Banks and Lending instituations
This is the third type of company. WellsFargo, B of A, and any other institutions that have portfolio loans are examples. Some of these will find agents in their own broker network to complete BPOs and list REOs. Others will contract with a BPO companies to find Realtors to complete their BPOs. It's case by case.
All three are worth pursuing. Completing BPOs is the best path toward gaining credibility in the REO listing world -- and getting your first REO listing.
PS: Check out http://www.LearnToListREO.com for a list of BPO company contact information.
My experience has been this varies by bank. But all banks have separate departments that handle REOs. When I've called about a house for a buyer, it's important to have the tax documents from the house, so at least when you call, you can get to the right department. The the house is listed, it's a whole lot easier. Or, if the house is scheduled for auction, you often can information from the sheriff's department. If you need help with a specific property, let me know, and I'll see if I can help.