Customers using Google Apps Vault can now activate the new Hangouts in the Admin console. An amendment has been added in the Admin console that allows you to activate the new Hangouts on acceptance of the terms. This amendment outlines the change in Vault functionality that will exist until Google completes the roll out of full compatibility. You will still have eDiscovery and legal-hold capabilities for your on-the-record/history-on chats, but the retention-purge function will not be available. To agree to the amendment, please log into the Admin console, go to Apps, click on Talk/Hangouts, go to Advanced Settings, and click “Enable Hangouts”.
For more information:
https://support.google.com/a/