The following new feature in Migrator for Notes to Exchange 4.12 and later will allow you to select the language used for "well-known" folders being migrated:
The Data Migration Wizard now allows you to specify which locale section (in its Task Parameters) to use when assigning folder names to Outlook folders. The value may be specified in a new program parameter in the [General] section of Global Defaults and Task Parameters:
[General]
LanguageCode=<String>
The default is null, in which case the wizard will use the section associated with the system locale (of the computer running the wizard). But if (for example):
LanguageCode=de
... the wizard will use the folder names defined in the [de] section of the Task Parameters.