No, the .NET support on xbox is rather limited.
WME core assembly is basically the engine (C++ code) with C++/CLI glue working as a bridge between WME and .NET. There's no way you can make this run on XNA/xbox.
Generally speaking, XNA doesn't allow you to leverage any existing C++ code, so everything needs to be rewritten from scratch in C# (and the result is not portable to anything but Windows/xbox).
