AHM communicates via ACARS (see Boeing Aircraft Health Management brochure).
ACARS is a data communication network, AHM is a set of data communicated on that network.
My understanding is that Boeing gets the AHM data whether or not the airline subscribes to the service. Yours is the first assertion I've read that AHM includes GPS data. Assuming that AHM does include GPS, my comment was just that the GPS data has to come from a plane-board computation, and I speculated that GPS computation might be turned off by the operator of the aircraft.
Hello again Cboldt. I assume that both systems use the same onboard transponder. They each must have their own processor that shares the transponder. The AHM, according to the Boeing ad, contains 160,000 parameters. That has to include GPS data. If not, it surely includes altitude, heading, and airspeed from the air data/pitot system. Did you see the just published photos of the 777 floating in the water off the coast of Malyasia? I am assuming the image is photo shopped.
I would agree with Cboldt. Boeing has a lot invested and exposed to lawsuits so they would be smart to store this data regardless of whether or not an airlines purchases the service. The cost of data storage would be miniscule compared to real liability a lawsuit would create.