IntelliSense Snippet Processing with Visual Studio 2010 SDK MEF Text Editor

Using the new Visual Studio 2010 SDK developing against the MEF framework the question is:

How can I use the MEF editor interfaces to handle fragment behavior in IntelliSense? It is ICompletionSession

not a problem itself (like getting the available snippets), rather filling the snippet, handling subsequent expected actions like tab, behavior input, text replacement, etc.

Is there a way to do this without a language service? By testing the built-in behavior in the base editor implementation of Visual Studio, they built the MEF interfaces on top of a set of language-based objects.