The interpreters can regulate conversation. For example, if you look at the Quebec election platform a few years ago, it was televised, and it had four sign language interpreters simultaneously working, one representing each party. They were neutral, obviously. The interpreters would just interpret the conversation happening back and forth, and it was quite effective. It's available on YouTube if you want to see a sample. That seemed to work very well.
On December 5th, 2017. See this statement in context.