I could not find this feature in the alpha version of Blender 2.8, nor could I find any information on whether the feature will still be available with the release. I only found a hint in Where is the Layers panel in Blender 2.8? where a responder said the interface for the layers is not yet fully implemented. Does anyone know if this feature will still be available with the new release? Thank you.
The 2.8 version is not released yet. Even the developers cannot be absolutely sure about how everything is going to be when it's finished. Ability to override materials per render layer is an essential feature. Even though nothing can be said with absolute certainty at this moment it would be very logical to assume this functionality or a way to achieve similar results will remain in one way or another once Blender 2.8 is released. Once again, let's remember the obvious one more time: at this moment Blender 2.8 is not meant to be used for production and is expected to have a lot of serious issues.