Although the title of this post may sound oxymoronic, bear with me.
One of the Japanese podcasts that I listen to is 日本経済新聞＜総合版＞ (Nihon Keizai Shinbun Sougouban), which focuses on economic issues in Japanese and is of course aimed at native speakers. However, after commercials, an American announcer pops in and says, "The news continues on Radio Nikkei." In English. For those of you who've spent any time in Japan, that's hardly surprising, but could you imagine the parallel in the States? If they threw the same thing into an English podcast in, say, Spanish, I'd expect that most people would have no idea what's being said and that's why it rarely, if ever, happens in the States.
I'm not convinced that everyone in Japan would know what's being said in this case, although I might guess that the subscribers to this podcast are probably a bit above average. Still, everyone in Japan has studied English; it's required in school. So, in theory, they should be able to understand it.
So here's an interesting question. If a foreign language becomes so well understood among speakers of a given language that they throw words, phrases, and even entire sentences from that foreign language into the dialogue when using their native language, has that foreign language actually become part of their own language? Think about it another way; if someone comes to Japan from, say, China, would they need to understand English to the same level as the Japanese do in order to understand what's going on in Japanese? They very well might. Indeed, the Chinese are a very apt example, because one of their trouble points in Japanese are words written in katakana, which are primarily from English and don't share the Chinese character roots that many Japanese words do.
Link: Nikkei Shinbun Podcasts (in Japanese)