I've been in alliances that speak 4 or 5 different languages as their natural language. It has always been the case that in those alliances the CiC decides that one language will be used for communication, be it French, Spanish, German, Italian, English or any other language and it is up to the rest of the alliance to use whatever translation tool is needed. They are always also told that if the translation was incomprehensible then they should ask.
By having one language the CiC can know that everyone is covered by one of two options - they either understand the language or the players need to translate it. imTranslator does a good job with most languages, even Klingon!