What's the Javascript story on the server side when we have real interoperability needs? For instance, in the corporate world where there are huge Java or .NET

What's the Javascript story on the server side when we have real interoperability needs? For instance, in the corporate world where there are huge Java or .NET libraries that I absolutely need to access with good performance. Is there an easy path to access JVM and .NET code with V8? And if not, has Microsoft released an interoperability story for the ie9 javascript engine? Clearly there is huge momentum with javascript as a dynamic scripting language, which probably is going to last a while given that the client side is going to stay javascript for a while. But I'm wondering if it can replace Jython/IronPython where those are needed.