What "acc position"? The I/S has an accessory position?
Yes, the ignition switch is different from the Standard. Many parts are interchangeable, but there is the extra accessory position on the interstate switch.
Rotate the top of the key towards the rear of the bike, opposite of the ON position. The LCD dash will light and the radio will play. I use it all of the time while working on or cleaning the bike....

Hay

Jimmyt