I assume that you have the RS 15-2103 to teach the others. There is a setup code for the Sony cable Cable_1006 but it is not in the 2103. It is in the newer RS-15-2116 that is also JP1 capable out of the box.
Having said that, I don't know whether it responds to discrete power commands or not. Most every Sony device that I have had any experience with have discrete power commands and they are usually the same commands 46 On 47 Off. (EFC's 113 and 109 respectively)
There is only one ccf file here for the DHG-M55CV and it does not contain any discrete commands because it is probably just be the learned commands from the OEM remote.
FWIW, I recently measured the power consumed by one of my Satellite STB's and it was the same whether turned on or off. Either way it was $4 /year. I think you will find similar results with any form of Set Top Box. So unless there is some other reason to turn it off, you may want to just leave it on.
