I'll soon be populating that wiki page based on the code that Neil mentions. It will include documentation on
how to turn on the realtime collaboration feature in the Blockly code and pointers to documentation on the necessary steps to enable those features in Google Developers Console (which is also necessary in order to use it).
Note that the checked-in code has the realtime collaboration features disabled by default. There's some more work to do before I would recommend enabling the code for production apps. I'll create some issues in the Blockly codesite to capture the bugs and feature enhancements that I know about.
If anyone wants to help with the work please feel free to contact me.
-Mark