I don't know if the stream URL changes when you put in a password so I guess maybe it you start the broadcast without a password and put a password maybe it's possible to still be connected to the stream but I doubt it as more people would complain about password shows being recorded.
The few times I’ve viewed a public broadcast and the model added a password during the stream, CB gives viewers a pop-up asking for the password. You can’t continue viewing the stream (in fact, I don’t even think you can stay on the page at all) without entering the correct password.