I have no idea who the "other bidders" could be. Frankly, unless it was another low cost carrier, buying YX would be a dumb idea. Well, dumb if your objective was to actually run the airline. I suppose NW could try to buy them to keep out AirTran. What a terrible deal that would be for Milwaukee, though -- I can't imagine anyone who thought about it for more than a second (except perhaps some mileage-addicted flyertalkers

) would think this was a good idea for either the City or YX's employees. It would be "St. Louis TWA" all over again. Plus, Milwaukee would lose the opportunity to get a first-rate low cost airline hub.
I also can't imagine any local group would be serious about buying YX. It would be a really dumb business move. Of course, dumb people do try to buy airlines sometimes.
What I think is happening here is YX management is being dragged kicking and screaming into this deal with AirTran. Logic isn't at play -- it's personal. They're looking at any alternatives -- even ill-conceived ones. At the end of the day, however, the compelling combination with AirTran is very likely to occur.