Tree Parsing in the Eclipse Modeling Framework with Ecore Metamodel

I am trying to write a plugin to the Open Source AADL Tool Environment (OSATE) which is a plugin to Eclipse to parse an annex sublanguage.  (AADL is Architecture Analysis and Design Language for embedded systems.  AADL allows definition of custom annex sublanguages for which OSATE will invoke a custom parser.)  OSATE itself parses AADL generating trees conforming to an Ecore/EMF metamodel defined using the Topcased graphical Ecore editor.  OSATE expects custom annex sublanguage parsers to generate EMF as well.

The example AADL annex sublanguage plugin uses ANTLR (v2) to define a parser which constructs an abstract syntax tree with tree nodes generated by factories automatically generated from the Ecore metamodel:

The hand-written example unparser tests EMF tree nodes using "instanceof".

I wrote a parser for my annex sublanguage using ANTLR v3 that generates ASTs of nodes that are a subclass of CommonTree, and an unparser using a tree parser that invokes string templates.  My test rig reads files, parses and unparses, and writes pretty-printed files that look great.

I can't figure out how to create an Ecore metamodel that implements the Tree interface so that an ANTLR v3 tree parser can walk them.  Ecore/EMF defines everything with its own E-objects (EClass, EPackage, EDataType, EString, EOperation, etc.).

ANTLR v3 tree parsers are perfect for testing whether an AST has a certain form or property, and for building a new AST while walking another one.

How can I get ANTLR v3 tree parsers to walk EMF trees?