The teleop.py node subscribes to sensor_msgs/Joy and publishes axis_camera/Axis messages. If you have a joystick, you should be able to control the PTZ using it.
The axis_ptz.py node subscribes to the cmd topic and receives the published axis_camera/Axis in order to control the PTZ unit.
In a nutshell, if you publish axis_camera/Axis messages from your node, you should be able to control the PTZ unit. I based myself on the teleop.py when I wrote my own node.