I was a language assistant, but not in Italy. It is what you make of it, if you are in a big enough place you can end up socialising with other assistants, but of the foreign people I knew, I mostly socialised with the German assistant anyway, so at least we did that in the language of the country that you are in.
I would say that the low point of the trip was that the school was really blasé about having an assistant, I was met my the librarian, who was delightful, and housed me for a few days, but the English teachers showed very little interest. I did not have a lot of prep to do at all, I spend lots of time in the classroom with the teachers, or they gave me small groups and very specific thing to do.
It is in a regular school, so there are naturally, other teachers of other subjects, I think it's easy if you are the sort of personality who will go and chat to people to get to know others, and to speak in the language. You don't have to really speak in English beyond those twelve hours. You get lots of free time to visit and explore, and the salary definitely enough to live on, once it comes of course.
I absolutely came back with a better level in the language than those who had spent time at a university, there was just no comparaison. But as I say, I made massive efforts to go out of my way to speak the language and not to socialise just with English speakers.
I also attended a RG university, and they interviewed us and ranked us before they sent our applications to the British Council. Perhaps that has changed but I would say that feedback is available, even if they cannont guarentee anything, they know what happens on a year on year basis, I don't remember finding out as late as June though, I remember it being sooner.
All in all, I would absolutely recommend the experience, but it is what you make of it. The huge, huge advantage for me was that the wages meant that I did not incurr any debt for the year. I'm still in touch with people I met then and it made an enormous difference to my language skills.