This article published by Le Temps explores the solutions to the tax dispute with the US from the perspective of Switzerland vs Liechtenstein.
The solution applied by Liechtenstein was to adopt an urgency measure approved by its government to transfer sensitive data about the US client to the USA. On the other hand Switzerland considered this solution, that was supported by a number of Swiss banks, to be legally unacceptable to Swiss standards.
As well as writing to the US Department of Justice (DoJ), the Swiss federal government then negotiated with the USA. It proposed a number of solutions internally and to the USA like the taxation at source of undeclared assets (similar to the Rubik solution in place with the UK), a Lex USA, to finally agree on a ‘program’, the US Program.