CPDLC is used in Australian, Fiji, NZ, Tahiti and Oakland Oceanic FIRs. It is also used on the Sydney - Jo-burg run.
I'm not sure what 'trial' you are talking about, CPDLC is always used (as far as I'm aware) in the YMMM/YBBB (melbourne/brisbane) FIRs when the aircraft is so equipped.
So far the only ones I have seen accept ADS are the Aussies, NZ and Jo-burg i.e. the others require you to push the "position report" button every so often (a major imposition).
To counter the problem of an aircraft getting a message intended for another aircraft, it is now a requirement to send a position report (even when ADS'ing) whenever you logon to a new center.
Jakarta (WIIZ/WIII) supposedly have datalink but I have never had the logon accepted.
HF comms in Australia are done by Flightwatch which I guess isn't really ATC, ATS I think they call it. HF in Oakland Oceanic is handled by San Francisco ARINC, a private company.
