iPhone 4 - Switching built in Apps - Google Maps versions
 

So I might get an iPhone 4 from mainland China.

Apparently though the google maps is one that has been customized so everything is labeled in Chinese (even say street names are in Chinese when you are in Paris rather than being in French).

Not having an iPhone...can I just download another version of Google Maps and use that instead?

In my experience using a Japanese iPhone, Google Maps will change the language of the maps based on the language setting of the phone.

That said, China might be a different case because there is actually a different version of Google Maps for China (http://ditu.google.cn/) which, in addition to being written in Chinese, depicts the official Chinese view of the world (including their unique interpretation of surrounding maritime borders)...

That is not true of the Chinese sold iPhone 4. On those the Maps App uses Chinese all over the world, not matter the user selected language. This is from personal experience, not something that I read on the internet.