Official Google Enterprise Blog: Bringing Google+ to work

Google+ for business, in "full preview" mode for now

"As part of this trend, we’re witnessing how web-based collaboration and social tools have dramatically changed the way people connect. Whether you’re across the street or across the world, you can hold face-to-face meetings, share updates with colleagues and friends and work on a presentation together in real time. Like Google Apps, we think Google+ can help colleagues collaborate more easily and get things done—and get to know each other along the way.
So today we’re launching an initial set of Google+ features designed specifically for businesses, and we’re excited to move into a full preview mode for Apps customers. During this preview period, organizations that have gone Google will be able to use the business features of Google+ for free through the end of 2013 while we continue to add more features and administrative controls designed for organizations. "

Official Google Enterprise Blog: Bringing Google+ to work