I'm in Canada, and I hear "Yes" a lot. "Line" is fairly standard, and it was what my uni classmates were taught to say. However, I have heard: various profanity, "What?", "Line please", actors who just mumble and "um" until I help them, to one actor who would just stare blankly at me. I have also worked with an actor who was older and beginning to lose their hearing, so I practically had to scream their lines to them. It was hard for me to do this, and not feel like I was yelling at the actor. That was interesting, as it was a large room and I already had to speak very loudly.