The US government's bid to halt Swiss bank UBS AG from aiding U.S. citizens to allegedly evade taxes has stretched from exclusive enclaves in Miami and Geneva to the highest diplomatic levels.

But a potential settlement in a Miami federal-court case, in which UBS has resisted U.S. legal efforts to turn over the names of U.S. clients, also could cast light on the detective work of Internal Revenue Service agents toiling in less-glamorous locales, including Richmond, Va.