I've used MUV when I forgot about vacation in the next month (the one beyond the current bid) and had it knock out a trip that went a few hours into the new month.
Not wanting to burn 30+ hours of vacation in February (or whatever crappy month it was) I did the MUV bid to knock some of that down. I limited my bid, however, knowing that whatever I got was mine, with no trading allowed. So bid carefully.