The ability of a voicebank to be fully compatible with another language without the need to record a significant (more than 2) amount of additional voice samples needed is called Automatic Compatibility. It is usually multilingual voicebanks that can achieve this capability, although bilingual voicebanks may do so as well.
Example: Voicebanks that are designed for a South-east Asian language. These include Vietnamese, Thai, Indonesian, Filipino, Malaysian. Historically their languages come from a single source.