Can enterprise App Read its MDM Configuration file?
As the devices are enrolled in an MDM server, I would suggest using Managed App Configuration:

https://developer.apple.com/library/ios/samplecode/sc2279/Introduction/Intro.html

Managed App Config was introduced in iOS 7 and allows the MDM server to 'push' a dictionary to the managed app's NSUserDefaults container, essentially allowing for remote configuration of the app.

As you already have devices in separate groups, you should be able to configure your MDM to assign different managed app configurations to devices in each group.