how bad do you want it-

If i was truly desperate i am sure i could figure out a way to intercept the voltage to the power LED to activate a relay to act as a trigger to my control system, and of course while i was in there i could probably add a few wires to the solder pads for the actual power button on the cable box so that when the control system intends for the cable box to be on it could essentially "press" the power button until the voltage to the power LED turned on.

you could of course also use IR to turn the box on but if i am already in there with a soldering iron i would probably just do it.

I doubt the cable company would be happy but then again i dont think anybody is going to open the box up when you turn it back in.