mmc8mmc8, I, too, have an MPF account and a company Provident Fund (ORSO Scheme), both being foreign retirement accounts. I pay tax on the earnings every year as well via "Mark to market." Regarding FBAR, I include these accounts if nothing else to be safe and transparent. It does not hurt to include them as no tax is involved.
I did a lot of research on this years ago but the only thing I can point to now for info. is the IRS FBAR Reference Guide:
Financial Account - "Any other accounts maintained in a foreign financial institution" and "A financial account is foreign when it is located outside the US." The MPF is a non-qualified foreign trust and you are a member with an account.
Financial Interest - "The US person is the owner of record or holder of legal title, regardless of whether the account is maintained for benefit of the US person or for the benefit of another person..."
There is also a "Filing Exceptions" list and I don't see anything there that would exclude filing for an MPF (a foreign trust).
I am no expert and there may be someone who can parse the language of this document to justify not filing for an MPF account. I welcome any information anyone else can add to clarify the issue.
One final note, you may need to file IRS Form 8938 Statement of Specified Foreign Financial Assets if the total value of your foreign financial assets are above the reporting threshold. This form goes to IRS while FBAR with similar info. goes to Dept. of the Treasury.