You have the option to set visibility permissions on each of your mailboxes in Groove. This allows you to only give certain agents or groups of agents access to those tickets.
You'll find these options down at the bottom of your mailbox settings page if you go into your account Settings > Mailboxes. There is a section that says "Who can see this?" with a dropdown menu next to it.
Here you can select between Everyone, Only Me, Select Users, and Select Groups.