Oreos are not vegan. They are not only processed on equipment that is cross contaminated with milk and eggs, but they use bone char to process their sugar. So they're not even vegetarian really.
I dunno about most of the other things you mentioned though.
In the UK sugar is not processed using bone char. And many vegans do not pay any mind to cross contamination during processing. If you use that logic you could never eat in a restaurant that wasn't 100% vegan.
No, a good restaurant doesn't do cross contamination. Well, not intentionally. I've known people that work in restaurants and freak out about cross-contamination. Of course, the same can't be said about those that haven't gone to school to be a chef or some such, because they just don't think about the issue.
But, an idiot using the same knife for meat or whatever is not the same as using the same machinery for two different things, and not cleaning it properly. Factory machines don't get cleaned nearly often enough, and they won't clean it out properly just because the next product is considered by vegans.