Also wanting this feature, please see here for the work i did, just need the final stages:
http://osticket.com/forums/showthread.php?t=8228(http://osticket.com/forums/showthread.php?t=8228)
We added a template for closed alerts and alert options for closed tickets Following the same structure as the other templates - we have added send closed alert to dept members regardless of assigned/unassigned status. It is located in the postReply() function.
Also, we added additional functionality into the customer postMessage() to alert dept members to a customer ticket reply if the ticket is unassigned. This required an update to the alert options and is using AlertDeptMembersOnNewMessageAlert().
I believe these are the two needed core features in 1.7. We are enjoying 1.7 btw...
Thanks.