I think what's needed here is a list of assignors.  If MERS assigned the mortgage to an outside entity, (ie to Deutsche Bank as trustee for a pass-through), which is common in Massachusetts foreclosures, then that particular assignee would be the correct mortgage holder with standing to foreclose.  If, however, MERS conveyed first to Deutsche Bank & then, later reassigned to BOA, without a recorded assignment from Deutsche Bank back to MERS, then there's a problem.  Within MERS who knows who actually holds the note.  There's no way to tell.  But once the assignment is on record to a non-MERS holder then that's it.  I have dealing with bad assignments on foreclosures for quite some time.  Fortunately, the banks are finally catching on to the concept that they need to practice good conveyancing.  The only thing that I can do is point out the problems I find to the closing attorneys.