This was stupid of the Bank of America, but how was it that they were even aware that this couple had bought a house for cash?
Having worked in IT in this area (just never for BoA) and my wife currently working in this specific area (home mortgages, though again not for BoA) we surmised the following as being the most likely scenario. Previous owner had a mortgage with BoA and title company screwed up somewhere along the line with notifying BoA that the house had been sold (could have been a transcription error on the deed number or a wrong address for the house or the mortgage contract number being transmitted incorrectly). Some time later, BoA is cleaning up from it's mortgage meltdown, and this house is listed in their database as still having an outstanding mortgage that has had no payments made in X months. So, they filed for foreclosure, and the foreclosure attorneys did not do their requisite title search before sending the forms on to the court.
Since apparently (from another source) BoA has at some point terminated their contract with the foreclosure attorneys in question, I'm guessing that they screwed up more than once, we just haven't heard about the other cases...