Taken from the the latest FBAR:
"IRA Owners and Beneficiaries. An owner or beneficiary of an IRA is
not required to report a foreign financial account held in the IRA.
Participants in and Beneficiaries of Tax-Qualified Retirement Plans.
A participant in or beneficiary of a retirement plan described in Internal
Revenue Code section 401(a), 403(a), or 403(b) is not required to report
a foreign financial account held by or on behalf of the retirement plan"
My reading is that if you have an IRA or 401(k) and part of your internal investment(s) is "foreign", (perhaps shares in an Indian rail road company), you do not need to report this "foreign part". The custodian of your retirement account have a preexisting relationship with the IRS anyway.
Going back to the subject matter. If you can dispose of the assets in the account by providing your signature, then it's reportable, it's your account, you own it... If you don't own the account or can't dispose of the assets as you don't have signature authority, then it's not reportable, it's not your account. The U.K old age pension is a good example, you wish to take benefit at retirement, but can't say to the government, give me all that money on my record!