If the English isn't dubbed then they're probably saying it for the show. Also it's possible to dub over with an accent. I'm assuming if it's dubbed, it'd be dubbed by a Chinese person so yeah there's going to be an accent either way. That's not proof of anything. The fact they seem to be speaking English to one another in the video is suspicious to me. Why would they do that? Why make it more likely to misunderstand each other. Also of course J-11 pilots hailing P-3s would be speaking English to the English speaking American crew of the P-3. That's also not evidence of anything.
I suspect it's dubbed because it just seems idiotic to me. It's not like Chinese people don't have their own language to use or anything. Radio already muffles your voice, combine that with pulling Gs, maintaining situational awareness, and having to do English to Chinese - Chinese to English translations in your head every time you want to say or understand something? Nah. These people are professional pilots not English teachers. Rudimentary English may be a requirement for certain PLAAF pilots, maybe even all of them, but there's that and there's only communicating in English.
