Thanks for the links. Unfortunately, that NYT article does not make a single mention of iMessage or end-to-end encryption.
Last I checked, iMessage still works in China. I find it implausible that China would allow this without access. If there's a mechanism for that, I'd like to know what it is and how far it extends. The fact that Apple doesn't admit that there's a difference in iMessage's security in China makes me wonder whether it is compromised globally.