Do companies based in non-English-speaking countries require intra-cockpit procedural communication to be performed in English?
This is common in many international airlines. 

Lufthansa Standard Operating Procedure (SOP) dictates that all flight procedural communication (checklists, standard callouts, etc.) are done in English.

The only "German" I've seen on Lufthansa's checklists is "handy .... off" in the pre-startup checklist (German English for "mobile phone .... off").