He's got a good point -- there are many studies of "Chinese learner English" which are intended to find out what errors Chinese learners of English make. But where does one draw the line between a 'learner' and a 'user' of English? Is a 21-year-old university student who has studied English since age 7 still a "learner?"
The Chinese corpus linguistics website www.corpus4u.org includes a post by a user which identifies the following corpora (in addition to SWECCL, which I've been looking at lately).
Corpus for English Learners in China (Gui Shichun, Yang Huizhong),
College Learner’s English Spoken Corpus (Yang Huizhong),
Chinese English Major Learner’s Spoken Corpus (Wen Qiufang),
CEC Chinese English Corpus (Li Wenzhong)
Middle School English Spoken Corpus (He Anping),
I don't know anything about Li's corpus (his definition of CE is frequently cited by Chinese scholars), but it is the only one that doesn't purport to be a 'learner' corpus. This list comes from a 2002 article by Feng Zhiwei on the history of corpus linguistics in China (read it here). He makes a point about EFL in China (though it could be applied to any 'expanding circle' country really) here:
The third feature of English corpus linguistics in China is its application-oriented tendency and intensive self-awareness. For years, most of Chinese research in foreign language learning had been devoted to the introduction and interpretation of western linguistic theories while there has been not enough independent research fuelled by the linguistic traditions of China. This situation had made it difficult for Chinese foreign language teachers and researchers to develop their own theoretical frameworks, and thus it had limited the contribution they could make to the international research community.
The applied research of corpus has now opened a new platform for English teachers and researchers from China on the international arena, to display their achievements, and to share and exchange their ideas by presenting the cornucopia of their achievements. Therefore, the intimate combination of corpus-driven applied research and the reality of English teaching and learning is a deliberate choice of scholars in the field of English language teaching in China that will propel corpus research in China and give Chinese linguistics an important voice in the international research community.
This is all well and good. The irony, though, is that many people who are advocating a more "China English" based approach to English teaching in China (that is, the one you'd think would be more homegrown) are working in "western-style" English-medium universities (mostly in Hong Kong), and world Englishes is a "western theory" in the sense that it originally came from linguists working in American and British universities.
Anyway, my real point here is that the purposes of research on traditional corpus(es) of Chinese learner English are, in a sense, "features-based," and WEs studies can also be "features-based." The difference is that the former is starting with a codified, authoritative US/UK English as a norm against which to judge the errors of Chinese learners, while the latter looks for possible innovations which are frequent and seem to be acceptable (by some). This is also Tian's point, I think. What if we took all the error analysis research, all the stuff about "features of L2 writers' texts," etc, flipped it, and started looking for innovations against a WEs framework? Isn't this what has been done for the Outer Circle? Why are we so reluctant to do the same for the Expanding?
Pang (2005) proposes a China English corpus that should "include texts that are published in Chinese official publications （journals, magazines, newspapers, books，CD－ROMs or broadcast through radios or TV channels）．English texts written by English learners at various levels at different schools, universities or training institutions do not fit the criterion."
This is interesting to me because, while it supports a CE corpus rather than a "learner" corpus, it doesn't entertain the possibility that Chinese university students can be competent users of English. Granted, I have worked with some of the most elite students in the country (I'm not trying to toot my horn, I just happened to be blindly thrust into teaching them one year), but I assure you that many of them are. What we seem to be coming away with here is the idea that there are two kinds of English in China: the "learner" English which is what every student does, and the "professional" English which is used by academics and the media. This has some merit to it, but it leaves out huge domains -- blogs, microblogs, message boards, business, creative writing, English corners (cf. Kubota on English as a hobby in Japan), etc. And of course the lines are probably not so well-drawn.