There is no official source on that which I could quote. But it is what I have been told by people involved.

There is another aspect, a lump sum of 5-15$ per unit might look like a lot of money for M$, but over a 2y period thats not much. All that such a deal would do is to make the phone a bit more expensive, same as if another earthquake hit and some parts like CPUs or RAM became more costly. Carriers would easily swallow that for subsidized phones. All the search revenue, App store revenue etc. would still go to others like Google. And most important, the customer would be lost to M$ - If M$ wants to take a significant market share in mobile, collecting royalties on Android is not the way.