This query is prompted by the report that ACARS was 'disabled' but that some sort of handshake was being initiated by the aircraft for several hours.
BOAC: The ACARS on the 777 is an integral part of the AIMS system. The data is collected and channeled out of the aircraft in 3 ways, VHF, HF, and SATCOM. The system allows one to choose the primary and secondary data paths, and it is here that one can disable it though the FMS CDU.
The handshake continued thanks to the SATCOM transceivers having been left on. They do not have a power switch, only circuit breakers. In addition, the radio pack is located above the ceiling fascia, aft, and not in the EE bay - so no easy direct access to the hardware.