I have read an article on the developmenet of the MS search engine, and their biggest problem to me was the requirement to build it on Window 2003 server. They have rewritten the server for the search cluster, but that still was a dead weight.
Politically, they just can't use Linux, that is clear to anyone. MS is even trying to stop their using the iPhone - by not paying for it.
However, if they work with Yahoo, then all bets are off. Even though Yahoo trails Google in search share with 11%, and their Hadoop sorts a terabite three times slower than Google's MapReduce, microsofties could have more freedom and more fun if that comes to fruition.