Nope, PMUTE definitely does not put the screen into standby, nice as that would be. My Panny 65" 9UK plasma has a diode pilot light on the frame which turns red when in standby; it remains green when PMUTE is activated. There is no relay click, either. The screen is connected to the PS3 through its RS232C port, and it does get turned on and off by the PS3, just like a BV4.
However, Max's suggestion led me to a solution. My screen does have a power management feature accessible through the setup menu. This feature places the screen into standby mode after about one minute when there is no video signal present. The manual states that this feature is functional only with the PC input, and I am of course feeding the screen from the PS3 through its DVI input. However, I gave it a try anyway and, much to my amazement, it works with the DVI input as well. Many thanks to both of you for your suggestions that caused me to find a solution.