What you have at your place are executives who don't want to make tough decisions. They want the decisions to be made for them. If they give Microsoft exclusivity over their I.T. choices, it makes their life much easier.
I suffer from the same things. We've been an IBM shop forever. Our managers have basically given all control to IBM to make our decisions for us. But we hired a new CIO. Not a friend of the mainframe. While we haven't abandoned the mainframe yet, its going to happen. Unfortunately, our CIO is making the same mistakes as the previous generation of CIO's. While he's no ally of IBM, he's had no problem going with Microsoft for everything else. So nothing has really changed.
I believe its really the culture these managers came through. In 10 years, we'll see more upper-level managers who accept open source or Apple technology.
I guess its really hard to find upper level management who believes in their employees. They are going to side with Microsoft over what their employees tell them.
My company hasn't listened to me ever. They only listen to IBM, Microsoft, and Gartner. Yet, when Gartner tells them the same thing I told them 18 months earlier, its like a revelation to them.