I'm fluent in Japanese. I listened to the beginning of the recording and it's legit. One of the voices is almost certainly Mark Karpeles' (based on hearing his voice in his recent public apology -- his Japanese is broken but reasonably proficient). It seems to be a recording of a Jan 30 2014 meeting where bankers from Mizuho Bank are asking Karpeles various questions about Bitcoin, the nature of his business, his partnerships in different countries, connections to underground activity, etc. Definitely not something that's meant to be publicly released.

EDIT: Listening to snippets from the rest of the recording, it seems that Mizuho is explaining that they want to cancel Mt Gox's accounts with the bank. Karpeles seems to be protesting and asking why the accounts are being shut down. The guy from Mizuho explains (at 28:00 for Japanese speakers out there) that it's a combination of a lot of factors, including recent technical issues, which make the bank uncomfortable dealing with Mt Gox. Karpeles also mentions following the orders of the Financial Services Agency (金融庁）

EDIT2: 15:00~16:10: Mizuho guy explains that the Mt Gox bank accounts will have to be shut down eventually. Karpeles says that he understands that position, but he thinks that the bank has been rude about trying to force the closure, and would appreciate a more cooperative approach.

EDIT3: 18:00~19:00: An awkward discussion of Karpeles' Japanese. The Mizuho person seems to be offended by Karpeles' rude Japanese, which frequently lacks the correct honorifics that would be expected in a business setting. A woman (I think she's on the Gox team?) explains that Karpeles' first language is French and that he means no offense.

I can work on a fuller description of the call, but just wanted to get a quick verification of its authenticity out there, along with some snippets of the contents.