Not sure on interchange, but i know they are hepco becker cases, which the same cases fit other bikes with brackets for those bags. So, stands to reason that other cases made to fit hepco becker brackets would fit on a Ulysses? I think lots of people have been building there own too. Now that you can get a Ulysses pretty cheaply its hard for someone to drop $800 dollars on side cases when a couple weekends and some ammo boxes will do.
Mine's got the "outdoorsman" top and side cases, also the same as the police package.