I successfully modified an M550SV today. All you have to do is remove the control panel and solder a jumper between either diagonals of SW1.
Edit 10/07/2013: This does NOT work… after about 20 seconds the monitor will shut off again. I found this out yesterday and am supposed to be installing 6 of these in the simulator tomorrow where I will no longer have access to this panel.
Edit 05/31/2014: I realized that I hadn’t updated what I ended up doing… I did a home-run of two conductors from each monitor to a relay which does a momentary (1 second) switch simulation. I was able to use just one relay with all of the positives from all of the monitors on one terminal and all the negatives of the terminals on the other.
Edit 06/30/2014: It looks like I did this for nothing – the monitors seem to power on when they detect the VGA signal from the computer… DOH
Edit 07/31/2014: Okay, I didn’t do this for nothing… apparently if the monitors shut off because they lost the VGA signal, they will come on when they detect the VGA signal. But if you lose power to the monitors they will NOT come back on without hitting the power button.