We're not doing anything special to help set up distributed Erlang at the moment. It would probably be difficult with App Engine because it's designed to manage stateless containers. But I could imagine setting up such a network with Kubernetes Engine, or definitely with Compute Engine VMs.
It currently doesn't do automated clustering of nodes out of the box. It should be possible to build a clustering strategy for libcluster (https://github.com/bitwalker/libcluster) for App Engine. Note that there's already a kubernetes strategy which could run on the Google Kubernetes Engine.