I work at proofreading scientific manuscripts in Beijing. The level of plagiarism is terrible. But I have also come to realise that a lot of people just don't know or don't care, so I gave up checking for such plagiarism. People that should be clearly aware of what constitutes plagiarism don't really know what is/isn't permitted or how to do it properly, and when informed of it they don't think it's a big deal.
Yeah, it's pretty horrible. I've worked for a Chinese publisher for 11 years now; when I first came, nearly everything in our books was plagiarized (and I work for what's supposed to be the TOP educational publisher in the country--HA). It's been a long, slow painful fight here, but after the first few years, my colleagues understood the view of the international academic community toward plagiarism, and after a few more years, they not only understood but joined me in The Resistance, as I've come to think of it. (I'm the "modern Lei Feng" of my department, ha ha) And it IS a resistance... I can't count the number of books I've returned unedited, with a long list of page numbers, passage titles, and internet sites from which they were copied. It's the passive resistance combined with the "I really don't want you all to lose face if this is published" explanation that wins the day. Now when I get a book, the first thing I do is a quick scan to see if my internal plagiarism sensor goes off, and then a quick google/dogpile search to confirm whether I was right. If I find something, then I pull out the fine tooth comb and start compiling a list of plagiarized texts/dialogues and the sources. Those lists are absolutely essential; my colleagues have no authority to argue with the bosses armed simply with "the foreign editor says", but when they can provide a physical list, giving sources such as CNN or the BBC or VOA, that gives the bosses pause. You just have to do it over and over, and over, and over... They'll get the idea eventually that you're not going away, that you're not backing down--and that you're not doing it to be nasty, but rather that you're just doing the job that they hired you for... helping them look good in the eyes of the international academic community. It's a long process of education--and really comes down to whether you're going to give up thinking it's useless and give in to the pressures to let them use you as the foreign editing monkey to put a stamp of credibility on something that's crap... or whether you start that passive resistance, smiling oh-so-nicely the whole time as you pass back unedited manuscripts with lists of plagiarized content/sources.
And, of course, there's always the tack that another editor friend of mine takes; when she does freelance editing, she'll give the Chinese publisher a few months to a year of "grace", informing them of the plagiarism she finds and giving them a chance to correct it. After that grace period, she'll just start contacting the original copyright holder directly to tell them the name of the Chinese publisher who's stealing their work. Whether you try my "educational approach" or the "whistle blower approach", choosing to do something is truly one of the kindest things you CAN do for those pathetic authors trying to pass off others' material as their own. The Chinese are trying to reach international standards, academically speaking anyway, but they'll never get there if they're allowed to follow their "traditional Chinese approach" to publishing.