Check out this link. I don't know if it links to the Interstate, but it looks like the Goldwing 1800 might.
http://www.sierra-mc.com/proddetail.asp?prod=SIE-SNA-GW-SR10Just to be clear for helmet to helmet my today choice would be Sena. I have Scala (Cardo) and they work great when connected. But require resets, fiddling with buttons, and relinking units. My G9's last around 9 hours while long rides are 12+ hours. When the ride ends in a strange city the loss of comms to the other bike is a pain. That's why the Sena is attractive.
Both manufactures offer great noise reduction and pretty good range. If longer range is needed you could use the cell phone to link or the Sena SR10 hub (multiplexer) to a radio (FRS, GMRS, Ham, CB, etc). Most can't tell I am on the bike when they call my cell. My G9 has great noise reduction and when the iPhone is used the noise reduction gets much better (go figure). But I will never buy or recommend another Cardo unit. When the G9's quit it will likely be Sena to replace them.
If you have multiple helmets then additional mounts can be purchased. Sena also has a unit for half helmets or no helmet communication.
In Florida we have noticed the Cardo units are not on display like they were.
Gil