I couldn't find any info about this and right now don't have a Smart Battery Case. As it's connected through the device's dock, the information about the model, manufacturer, etc can be retrieved using EAAccessoryManager, but nothing about additional data (for example, battery level). Studying the documentations wasn't helpful. Is it possible to get the battery level of it?
The answer is no, the Smart Battery Case doesn't provide it's battery level. It doesn't send any data to the app, except first time when it's connected to the device, sends some trash data.