How to access files from iOS AssetCatalog?

I'm using App-Slicing (one feature of App-Thing) to assign different assets for different devices, e.g. PVRTC Textures for iPhone 5s and ASTC for iPhone 6s.

The problem is that in this solution I found not way to access(read) files that isn't packed into any AssetBundle. File.Exists("res://file.txt") return false, and WWW("res://file.txt") or WWW("file://res://file.txt") doesn't work too.

I think pack these files info AssetBundle and using AssetBundle.LoadFromFile("res://file") may solve the problem, but bothers a lot.

So, is there any way to read those files in AssetCatalog directly?