Here is a comparison of a map area in iOS 6 maps that will look different depending on whether you are looking at it from China or elsewhere:
Outside China, Inside China
Other things to note:
1) Its not using Apple cartography, or at least it is different from the cartography Apple uses elsewhere. I'm betting its AutoNavi's cartography, since many Chinese map services mimic the Google Map style.
2) Its not using vector data, it looks like its using tiles, like the "old" maps. But it seems to load faster than the old ones.
3) Both Google and Apple are using AutoNavi in China (both screenshots below show attribution to AutoNavi). Apple shows more data at higher zoom levels than Google, it may even have more data for some reason. This is also a random small town, in case you want to know how detailed data is:
4) It follows PRC geography. Note the 9-dashed line that represents China owning most of the South China Sea, and another dash to include Taiwan:
Going to look at North American data from China also reveals much sparser maps, with hardly any data.
The flap reveals that data comes from AutoNavi, as opposed to TomTom elsewhere.
The map sources link also goes to a different link:
http://gspsa21.ls.apple.com/html/attribution.cn.html