Show mobile for IE only?

Jetpack includes a filter named jetpack_check_mobile that will allow you to overwrite the default Mobile Theme behaviour:
https://github.com/Automattic/jetpack/blob/3.1.1/modules/minileven/minileven.php#L30

You can then check for the phone platform (Windows Phone 7 or Windows Phone 8), and set jetpack_check_mobile to return false for these 2 mobile platforms. You can find out how we detect User Agents here:
https://github.com/Automattic/jetpack/blob/3.1.1/class.jetpack-user-agent.php

I hope this helps.