I too was looking at this, after finding that oddly MR's supported radsec, but the MS did not. C'mon Cisco, why such disjointed feature parity? So much for consistent integration.
Is there any projected timeline that MS will too support Radsec? I am looking at using a radius SaaS that supports radsec, but then found MS doesn't seem to actually let me, which is actually my main use case for wired 802.1x more than wireless.