A British friend of mine has managed to somehow get access to the e-Channel lanes on the mainland China side as well as the HK side of the border. I'm pretty sure he's not a dual citizen (he's neither ethnic Chinese and nor was he born in HK), and he's mentioned having problems when trying to subsequently exit China from somewhere that doesn't have the e-Channel lanes.

I'll have to ask him about how he's managed to pull this off the next time I talk with him.