Despite having been a civil engineer for 36 years I’m always in awe of these projects. I’m happy to admit J wouldn’t have a clue where to start!
China certainly seems to know how to 'go big'. The way things are going, there's little doubt in my mind that they are going to eclipse USA sooner or later as the world's biggest and most dynamic economy. I hate to say it, but perhaps *not* letting the free market & capitalism run amok at Tiananmen Square has brought about this result: lots of centralised planning and execution (erm, sorry, that might be a downside, in another meaning). I still remember the figure quoted in the BBC programme 'Beyond The Clouds' that China has one *million* villages. I can't even start to wrap my head around that, or how you govern it.
I guess the industry builds on previous expertise of specialist teams, whether that's native or foreign (until you've got native expertise). In two completely different examples, the Perpendicular church towers of Somerset of the 14th-16th centuries appear to have been built by a few specialist teams; and in my bit of France, a significant tunnel (les Grands Goulets) was done by an Italian tunnelling company (this, even in the early 2000s), rather than the local design & build outfits for more minor projects.