There still remains some WP Engine specific code related to early development to integration with network (Varnish) caching on the WP Engine platform. This exists as a hook that listens to the purge functionality and calls some WPE specific code that only runs on that platform in that WPE plugin.

Removing here and working to make sure it doesn't break behavior for WPE users. That code, or similar actions, should exist before this issue is closed.