Is there any app allowing to track buses and other types of public transportation (at least large cities of) mainland China, which has an English interface? I assume even if one gets Google Maps to work, they won't be showing routes and schedules.
It's likely city-dependent at present. For example, the Beijing Bus App for Beijing seems to be scoping to do that and more.
I use a WeChat mini program called 车来了 (as mentioned on another answer). You just enter the bus number and it shows you the real-time route information, incoming buses and estimated arrival time which is pretty accurate — in my own experience. If you do not have WeChat, you can download it from the app store.
You can also download the navigation app 高德地图. Simply enter your destination and location, click the mode of transportation (for buses and subway, choose 公交) and it will show all the available modes of transportation, route information as well as estimated arrival time. (Sometimes the 车来了 app does not show any incoming buses when the bus is still operating, I use the navigation app to double check.)
Unfortunately, the two apps do not have an English interface, but in my experience, their visual guides are simple to understand.