Here is a PDF that details the System Center 2012 Licensing model which has been brought in line with Server 2012 Licensing.
Microsoft System Center 2012 is a comprehensive management platform that enables you to more easily and efficiently manage your IT environments, including your server infrastructure and client devices.
With System Center 2012, you get the most cost effective and flexible platform for managing your traditional datacenters, private and public clouds, and client computers and devices.
System Center 2012 is the only unified management platform where you can manage multiple hypervisors, physical resources, and applications in a single offering, versus multiple fragmented point solutions delivered by competitors.”
Two editions Standard and Datacenter
Processor based license which covers two processors
All components included in both versions