I seem to recall the rumors about Microsoft acquiring Nokia some months back boiled down to an agreement they came to regarding such an event.

Specifically, it says that if a company offers to acquire Nokia, Microsoft is allowed to match it. If the offer from Microsoft and the other company match, Nokia has to accept Microsoft's offer.

This is in place just in case someone does come along and tries to snipe Microsoft's plans.

And no, I don't think MS will buy Nokia. My conjecture regarding their plans is to ensure that if things go badly, Nokia eats most of the losses instead of Microsoft. That would be defeated if Microsoft took ownership of the company.