I really hope this post doesn't get lost in the fray, as I have a unique perspective on this issue-- a very similar thing has happened (albeit with fansub scripts) to myself and to friends of mine a handful of times.
First of all, this is not a coincidence. Translation doesn't work like that. A =/= B 90% of the time. If the lines were extremely short and basic, I could see maybe 40% as being within the realm of possibility, but 50% or higher is just... indefensible.
Second of all, as has already been stated here, it's important to acknowledge that Squenix staff might not even know this has happened. It's absolutely possible that the person they contracted to do the Italian translation themselves ripped off the fan translation to snag an easy pay cheque.
Lastly, yes, this happened to me and several of my friends. Fansub scripts that we had made showed up on official DVDs. With regard to the legality of doing this, as it was explained to me, we had no discernible recourse. Our work was a derivative work for copyright purposes. We didn't own it. The holder of the copyright of the work from which it was based owned it. And also, this happens way more frequently than the amount its brought up in the public sphere would suggest. A couple years ago, a toy manufacturer who shall remain nameless showed a trailer they'd cut at an industry convention-- someone posted some off-screen footage of it, and lo and behold, it was all made with fansubs. In the same series, the English localized script was based on those very fansubs. I brought the story to some industry friends who told me it wasn't news. It happens all the time. A year or so later, a TV channel in the Philippines licensed a couple of those series for their own English dub-- of course, the scripts are the fansubs to a T. I don't know any fansubber who's been in the game for at least a decade that hasn't had something like this happen to their work, or had it happen to a close friend. As far as my admittedly limited grasp of the law is concerned, all of the above parties have every right to do this. My little rinkydink fansub script is infringing on their copyright. Hell, it's the clean hands doctrine. What court is gonna award me anything for stealing?
Some of the people who worked on those scripts were upset, but frankly I was flattered and I put it on my resume. I can prove it's mine, after all. Assuming EU law doesn't differ greatly with regard to ownership of the derivative work, which admittedly it just might, I recommend these Italian translators do just that. If your work is good enough to steal, it's good enough to get you hired.
EDIT: I guess it's important to clarify that I am not a lawyer nor have I consulted one with regard to this issue. I could be completely wrong about this, and I'll own that. I also definitely have not so much as an inkling of where EU law stands on this subject.