This seems similar to what Jeff Dean was working on with AutoML: https://research.googleblog.com/2017/11/automl-for-large-sca... . Is DeepMind collaborating with the Google Brain team and how connected are the teams? It seems somehow that the efforts may be duplicated in some areas...
- AutoML is used to automate the design of the ML model.
- Population-based trained is used to automate the choice of the hyperparameters (e.g. the rate of learning).
If you wanted to use both, you'd first use AutoML to find a good design for your problem, and then you'd use PBT when training your network.