From swissblawg4A_340/2015: International judicial assistance in civil matters; bank client confidentiality (official publication):
The Federal Supreme Court holds that persons subject to bank client confidentiality cannot invoke the right to refuse to cooperate pursuant to Art. 166 para. 1 lit. b CCP, but as “bearers of other secrets protected by law” may only refuse to cooperate pursuant to Art. 166 para. 2 CCP, i.e. only if they credibly demonstrate that their interest in secrecy outweighs the interest in establishing the truth (E. 3.1.1).