No Language Barrier
Can't be helped.That's not surprising.
Chinese pilots flying in their own China airpsace using Mandarin. It is so-so-so common using Mandarin. Ask the PanAm Flying Intructors here, they will share with you lots of things.
China and India are the real big player in aviation market. There will be more planes from China coming in to U.S. So, ATC has to show tolerence to them.
I knew a Swedish, who speaks little English. His accent is just sounds like a Chinese. That's only a faceless media, nobody knew whether that pilot is a Chinese not (although it is AirChina). Don't forget, there are lots of expats pilots in China (some of them are in this forum). These expat pilots do not speak English, still China's air operators are opening door for them. Who cares?
In Taiwan, the ROC military pilots (interception) are using Mandarin too! In fact, many control towers are using Mandarin.
In India, some Indian pilots do use Hindi and Tamil languages to communicate!
In Thailand airspace, Thai pilots using Thai! Thais do have problem in understanding English, they choose to speak in Thai. Hah...their communication can be heard very clearly. There are expats pilots working in Thailand, they should be able to tell you more on this.