Andy:
Yes of course you can use whatever radius server as a AAA server for 802.1x authentication on the switches. NPS, IAS, ACS, Open RADIUS ....etc.
If you have problem with configuring the IAS then I would suggest that you post your quesiton in a microsoft forum and not here. They would be able to better assist you with your issue. But you can still look somewhere in this forum or in google to help yourself.
See this link, it could be useful for you: https://supportforums.cisco.com/thread/2090403
Regards,
Amjad
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