I'm pretty sure Disney is the one who handles the voice acting translation.
Or at least is the one who is paying the actors since people like Billy Zane, Christopher Lee, and Leonard Nimoy probably wouldn't just give their voice away to any video game company unless they backed by a giant like Disney. ( Not saying Square Enix isn't a giant but these guys probably hardly acknowledge them )
Square Enix does all the localizing themselves. It's obvious if you've been following their games - they have a pretty distinct style. Things to look for are badly localized jokes followed by silly laughter, solid but "safe" acting, hammy villains and a high degree of pretentiousness that makes you go "please just loosen up a bit!"
Disney probably contributes on the economical side though.
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