Sorry to double post, but I thought this data has something to do with our conversation:
Japanese working overseas, and overseas workers in Japan | 世論 What Japan Thinks
Check out Q8 and all of its parts. According to the Japanese surveyed, a foreign worker's Japanese ability is obviously important. Understanding of Japanese culture and customs was above "specialist ability" (which I'm assuming is one's ability to perform in a job). I think that says a lot. The people surveyed are people interested in working abroad, so I'd imagine them to be the more relaxed type when it comes to those things.
I'd bet that a Japanese person's opinion on ability to do a job is directly related to a person's understanding of their culutre and customs.
As an aside, I found it funny that nearly 25% of the Japanese surveyed claim to be able to at least "get by on a holiday without problems". 95% of the people surveyed have never been to a foreign country (I say "been" because their opinion of "living" can happen in less than a year). Beyond that, over 8% of the people surveyed feel they are able to do everyday conversation and beyond... Granted those surveyed had an interest in working abroad. Those numbers seem a little confident.