No, but in every one of those cases English is the way to bet.
> What about a Belgian company from Wallonia and a French partner? Or Luxemburg and Wallonia?
Almost certainly French because it’s the working language of both companies. If people share a native language they’ll use that. Otherwise the default is English. It’s not certain that they’ll use English but Siemens doesn’t expect its international partners to have German speaking partners for dealing with it; it does expect its executives to speak English.
Just as science has a lingua franca so does business. It is English.