First, my translation:
"As a result of the discussion, office and dining hall became non-smoking area"
I think that in this case, ことになった isn't used in the sense of 私は出張することになった。=> It was decided that I make the business trip. Instead, I think that it is more 禁煙ということ+なった. "It became a non-smoking thing"
I might be wrong though, because I must admit that I still have quite a lot of issues with という. It's not that it would hinder me from understanding a sentence (at least in most cases), but it's still kind of a blackbox for me, since I can't really detect much regularity in its use.