I think that usually the registration audits are conducted in the native language of the company/country, or an interpreter is present. I know that the ability to speak spanish was desired for auditors in the US, with the growth of manufacturing in Mexico. I have seen many registrar audit checklists with a space for "language of audit".
I have worked with a few multi-lingual clients. I will have some of the important, company wide documentation (such as the quality policy or critical work instructions) translated, but not the entire system. We rely on training instead of documentation in these systems also.
I just completed software training for a multi-national company with a plant in Mexico. The original documents were written in English by their US corporate location. Their Mexico plant translated them into Spanish when they customized them. I don't think they were planning on keeping "controlled" versions in English, but they might since they do have some Americans that go down that can't speak Spanish. Most of their on-site management staff is bilingual. All of the work instructions (at every work station) were in Spanish with lots of pictures.
One of my clients had a pre-assessment audit and the registrar sent three Japanese auditor trainees to witness it as part of their RAB requirements. They also sent an intrepreter, but I never heard her say a word. I don't think they understood anything that was going on, but apparently it still counted for their witness audit requirements.
