Yeah, you're right Tony.
and in addition the chip in the Empeg that does the "IR sensing" is a Crystal Semiconductor chip that specifically supports IRDA and Consumer IR on board the one chip [just set the registers up on the chip and it works].
I'm not sure about the "output" side of the Ir signals for consumer Ir though - i.e. whether the consumer Ir capability is supported as-is.
However, you certainly can fake it though using the correct IRDA data streams. This lets you emulate most 38Khz consumer IR devices.
However, you're possibly talking some serious coding/testing to get all this working right, but if you could, it would be worth stuffing into hijack, or even as a "add-on" application.
The other thing is that the IR emitter in the Empeg is designed for a 1 meter range as per the Irda specs. This may not work very well in the car environment when talking Empeg to other Head Unit and relaying on simple reflection, you may need a "ir to ir" link of some sort quite close to the Empeg to maximise the Ir signal strength.