Microsoft may (actually I think it will) in the future release the IE10 Chakra (JScript engine) as a stand alone module, like google V8 JavaScript Engine.
C# and IronPython are both .NET languages. They share the same run-time, so they can interact easily. There's nothing to suggest that Chakra is built on .NET; rather, given that it compiles the JavaScript to machine code for the sake of performance, I'd say that it won't integrate in the same way.
They might provide a .NET API that would make it possible to pass JS from a .NET language to the JavaScript engine, but that's just conjecture on my part.