You might have to go at that one backwards.
First, is it illegal to carry a collapsible baton? Any regulations or prohibitions at all, OC or CC?
If it is regulated or prohibited, does the CCW statute expressly exempt a collapsible baton from the regulation or prohibition on the part of permit holders?
If the CCW statute does not expressly exempt a collapsible baton by name from an earlier regulation or prohibition, then I'm thinking the door is open to interpretation--by the cops and courts. Meaning a cop could say, "Aha! A collapsible baton is not a billy club, therefore you are illegally carrying a collapsible baton. Put your hands behind your back." And, a judge just might agree with the cop. That would be a little too open to interpretation by cops and courts for my comfort.