You can CC other users to become followers on your ticket and receive notifications.
To do this, simply CC your colleague(s) when replying to the ticket email notifications. This will automatically add them as a follower on your ticket and they will receive ongoing update notifications from then on. These tickets will be visible to users by selecting the 'View Tickets I'm CC'd on' option in the ticket view section.
Currently, you are unable to CC colleagues at the point of ticket creation, however, we are hoping this functionality will be available soon.