I have been finding nothing but mixed answers on this. Some forum replies and the Tera Answers reply said no, GvG is not available on PvE servers. However, in game I have had several people reply and say that yes, GvG is indeed available on PvE servers (but limited to certain zones and mostly towards cap).

Can someone please confirm or deny whether PvE US servers, like Dragonfall, have GvG or not?

I can't find it now, but there was a post by one of the developers that stated there will be GvG, and deathmatches, and all that good stuff on PVE, the only difference is, on PVP, u can gank people

Yar, I believe this is what you are referring to: https://tera-answers.enmasse.com/posts/f1479ab5ea

Do we know whether they have already been implemented yet, or are they still listed as "on the way"?

it was on the PVP forums under barracks, can't find it now, but its very similar to that listing, its not yet available but they will be bringing it

Ah, gotcha! I appreciate the response then. :) Shame they haven't specified a general timeframe. Be nice to know if they meant in the next month or by Christmas lol