Most bank owned properties allow a 2 week window for all offers to come in, then all offers received will be submitted to the bank for review. The top 5 or so will usually be countered back for your "highest & best" offer, and then the acceptable offer will be chosen based on the counter offers received. It is important to really present your best offer as bank owned properties are mainly concerned about receiving the highest sales price!
Good Luck on your offer!
What I've noticed is that some banks will take a few days to respond and others don't even look at offers that come in the first 7-10 days. Its a way to get as many interested buyers to submit their offer. Generally getting multiple offers. A win, win for the banks. I know its frustrating. Good Luck!