In the style I train, we have tanto waza for shodan grading the first time and we use a live blade. As far as I know, there have been no accidents. But with the wooden tanto, I have witnessed twice people getting cut on the forehead. Both had no severe wounds but scratches. I think with a live blade you are more aware of the danger, especially in a testing situation. Last december I got the chance to view a sandan grading and there you have to do bokken techniques. We don't have a katana.
Hope that's what you are looking for.