Our 6 button scene switches (38A00-1) have a built in IR receiver designed to work with our IR Scene Switch Remote (38A14-1). I don't know about the Harmony's learning capability or if Logitech provides the HAI IR codes, but with my Pronto the HAI scene switch was in the database so it was a piece of cake to control it.
The Pronto also supports the HAI IP protocol for more complex actions and to allow status feedback, but if all you want to do is trigger a scene or something the IR works great.