Well, in the scenario I described (a London street scene), the logo would not be the main item in the photo. The photo shows a street, that happens to have a bus in it, and the bus happens to have the logo on it. In other words, the logo just happens to be there. I agree that if you took a photo specifically of the logo - if the logo was the central part of the photo - that would be breach of copyright.
As far as your point about commercial use is concerned, I'm not aware of any provisions in copyright law that distinguish between copying for commercial use and copying for other purposes. In general, if you reproduce and re-publish any copyright material, you are in breach of the law, regardless whether you do so for "commercial use" or any thing else. (Of course, we are not talking about taking a photo purely for your own private amusement, which nobody else would see. The important point is the publication of the photo.)