Scrum.org has been working for a while on expanding and bringing more structure to the original ideas on how to scale Scrum brought forth in the book Agile Project Management with Scrum. Now it has launched a Scaled Professional Scrum course and Scrum Practitioner Open Assessment.
The Scaled Professional Scrum course covers scaling agile concepts and Nexus in particular: “Nexus™ Framework and approximately 40 practices which cause the Nexus and your scaling initiative to operate predictably.”
The Scrum Practitioner Open assessment complements the other many provides assessments and allows you to benchmark your ability to participate in a Scrum team, with focus on multiple teams engaged in a scaled development initiative.
Here is a nice interview with Ken Schwaber at InfoQ: http://www.infoq.com/news/2015/03/assessment-program.
I will be coming back to this topic with in-depth analysis and how it compares with other frameworks. For the moment, let us just say congratulations to all who have contributed to the effort. 