For all practical purposes, tax information exchange agreements are completely useless. Signing one is a complete waste of time. You will discover that some place like Jersey, which has 50% of its economy dependent upon financial services and has had a TIEA with the U.S.A., for example, since 2002—one of the first there was—has so far exchanged less than one hundred pieces of information on $400 billion worth of assets located in Jersey.
For all practical purposes, that means they are absolutely impossible to use, and even when information is supplied, the quality of that information is normally very low, because you have discovered that actually the bank does not really know who the beneficial owner of the asset is.