Converting a project from .NET to .NET/WinRT is easy if you're not using Pinvokes or unsafe code because most of the classes are still there and work the same.
Silverlight, maybe but there are substantial chunks of .NET that don't appear at all in the WinRT world, especially if you aren't using WPF for UI. Of course if you're using Win7 compatible hardware then it's not really an issue, since you can run the exact same .NET application in Win 8 without any porting whatsoever.
WinRT is a programming framework and Metro is a process-style, so I'm not sure what them having a "remote wipe facility" would even mean. But Windows8 has a restore to factory settings that is accessible locally (and which an admin could probably script remotely if they really needed to).
I think the point is wiping/disabling the device if it's lost or stolen. Windows devices will naturally have access to all the management tools used on laptops today, such as DirectAccess and SCCM, so no need for new tools or retraining. Managing a large scale deployment of iPads in a secure way is considerably more difficult.