Comment 29 for bug 427846

xrandr isn't the right package for this. The xrandr utility is not a daemon process, and so doesn't handle any hotplug events.

On gnome, monitor hotplug is handled by gnome-settings-daemon, so possibly this is a bug (or missing feature) in the corresponding kubuntu tools, but I don't know offhand what that is so I'll leave this filed against xorg for now.