The SATCOM units on 9M-MRO were actually the Honeywell/Racal (Honeywell/Thales) MCS-6000 SATCOM Units (per the Malaysian MOT Interim Report
) as pictured below,Radio frequency unit (RFU,left), satellite data unit (SDU,center), and the high power amplifier (HPA,right).
The manual above is for a later generation but they are extremely similar.
The factual information document
provided by the MOT provides some additional details including a Boeing schematic (see 1.9.5 Satellite Communications (SATCOM), pages 48-50).
To answer you question, yes the SATCOM can be indirectly disabled from the flight deck by isolating the left main electrical bus (See this document
). This is not as simple as flipping a single switch but it is not terribly difficult either and pilots would have no problem in doing so (Also see http://meriweather.com/flightdeck/777/fd-777.html
I think the more important question though, is would the pilot have known (or made an effort to have known) that the AES was supplied by the left bus, and if not was the temporary disabling of the AES a side effect of the pilot's attempt to disable something else? I.e. What was the pilot really trying to accomplish by isolating the left bus? The answer could involve the flight deck door.