Still down.I noticed that if I let the install of Phoenix Core Services time out, it eventually fails with the message:
Plugin Install Progress: Done - FAILED - Dependency Install
phoenix-api-FAILED - Dependency Install jsoup-FAILED - Resource
So my guess was right: the plugins are hosted in the same domain, probably on the same server(s). If Google has pulled the plug, then we need to find an alternative source of the required files to repair these broken systems.