If they did, it would be all the more reason to dislike Microsoft. And if they were caught they would be in big trouble, potentially legal trouble. They've had enough monopoly trouble that they likely wouldn't do this.
Your average search engine user has very little technical knowledge, and implementing an idea like that would be useless, as well as giving certain companies an unfair advantage.
No. A search engine's only job is to return the most relevant results to the end user. Adding in any form of bias towards the technology or hosting will potentially mean poorer results are placed higher. So, no.
You could just reconfigure the Apache server so it says it's IIS. Changing the Server: header isn't rocket science. Try it, see what happens. Enquiring minds want to know.