FC summoning of Primals in PvP was a feature announced long ago for the game back before launch but nothing has really been mentioned about it lately so I can assume it's probably been quietly dropped (most likely due to the development team simply being unable to make it a workable concept that doesn't break the game's balance).

Of course I'm happy to be proven wrong though, but given the fact I haven't heard anything mentioned on the subject lately, I'm liable to consider that SE have scrapped the idea.