For translation, I use a translation service that requests we submit a .po file of the content to be translated. Is there any way to export a PO or MO file for a survey that I can submit, since this seems to be the preference of most companies? I can find where to get a .po file for LimeSurvey itself, but not for the questions of a single survey.

As far as I know, there is no way to export the survey texts as .po file. But most translators wouldn't even know what a .po file is..