Not quite, though my previous response wasn't correct either. Having done some further research, I realise that the "standard" ATC language for a country is that country's official language - so French, Spanish, French etc. are standard if the country uses them as its first language. However, any communications in English must be responded to in English, so you can reasonably assume that any ATCO at an international airport will be able to respond in, and understand, English. Going back to LFPO, this means that French is totally legitimate language when flying into there, however you don't need to know any French to fly there; if you start speaking English on frequency, someone will be able to reply in English too. As far as I can tell, this wouldn't be expected of languages other than the host nation's and English though - E.G. you couldn't fly into Orly and speak Chinese on the radio and expect someone to understand you.