Interesting wonder why they listed RT 12 in the law suit, just wondering used to live down that way and still work in the area.
They probably wanted to file suit in Chicago. The federal courts in Chicago (the U.S. District Court for the Northern District of Illinois and the U.S. Court 0f Appeals for the Seventh Circuit) have had a lot of experience handling complex patent infringement cases - including some involving snowmobiles. In order to file suit in federal court in Chicago, they needed a named defendant who "resides" in the district. Route 12 Rental is in Cook County, IL. Arctic Cat will probably defend and indemnify the dealer, so its really probably just a technical legal matter for jurisdiction and venue.