Does anyone know if the stock pioneer headunit has the same IPBUS controls as the retail aftermarket headunits do? In theory if so then what is to stop someone from buy aftermarket XM componets and antenna at a FRACTION of the dealer price. If you ask me $500 is very pricey for XM... and I wouldn't do it now perhaps in future.

Thanks for any insight or suggestions.

No it doesn't, it uses Toyota's plug. You will have to replace the HU to go with and "aftermarket" XM receiver if you want to pay less. We had another post similar to this just a day ago.