Its definitely not 100% perfect subtitles but you can make out 90% of whats going on.
Helps if you remember the back story and the context of what they are "trying" to say when the subtitles are not correct.
I guess this will be the best to go around unless someone uploads the actual Sky Atlantic screening with Sky's english subtitles.
And you're right about the Neapolitan dialect - I have a friend from Verona and he has no idea what the fuck they are saying haha, he needs english subtitles too.