As Dameon mentioned, this is possible and configure via the policy in the management tab in the account's SandBlast Cloud dashboard. Under the 'Email Destination' box within the relevant rule you can select the destination mailboxes (or "who this rule applies to") configured per the O365's AD groups.
Make sure that you also have a relevant license for the amount of mailboxes and that you have associated the license.
For more information on this or anything else related to SBC, feel free to refer to the step by step guide. The latest version can be found in the POC guidelines: TE wiki page under 'Best Practices and Cookbooks'.