Do corporations outside of the Eurozone issue bonds in Euro?
Answer by @Wecon in the comments:


  With respect to your first question: they certainly do. The BIS quarterly review of sept. 2015 (p.9) even shows that "firms in the United States increasingly issued euro-denominated debt to benefit from the low borrowing costs." This may already be a set-up for answering your second question: its (relative) importance may be highly dependent on economic circumstances