According to a post (5/26/2011) I read in the AutoCAD LT Discussion Group Object Enablers for AutoCAD Architecture and AutoCAD MEP are now built into AutoCAD 2012.  This info was posted by Kate Morrical, AutoCAD LT Technical Marketing Manager, Autodesk, Inc. *Some Object Enablers are build-in.  Visit http://www.Autodesk.com/oe to get a complete list of available object enablers.