In considering cases like that, I wanted to clarify (to myself at least) how exactly {be} works, and in doing so wrote a post to the mailing list some months ago, which I thereafter consolidated into an article on the wiki. My understanding of {lo broda be ko'a} is exactly the one given in the article.
http://mw.lojban.org/lmw/Advanced_Place_Structure_ManglingI also think it's the most consistent understanding of how {be} works, since it doesn't invoke any magic, and it is basically exceptionless.
.i mi'e la tsani mu'o