As a follow up to the earlier issue I posted (Irreconcilable Differences). The inability to place these two types of objects using the Beam Command is limited to the command itself.
As a workaround for now, and allowing you to use the intended structural categorized objects and structural template based families, just drag a new instance of the truss family into the Drawing Window from the Project Browser to bypass the Beam Command itself. I wish I thought of THAT!
Thanks to Don Falkowski (Autodesk Revit Support) for chasing this one through and offering up a solution! It should be fixed in the next release, Thanks!