Hi there,
I guess that this following modifications will solve your problem?
(New Message Alert for All Department Members in osTicket v1.6 RC5)
(New Response Alert for All Department Members in osTicket v1.6 RC5)
Please note that those MODs being intended for v1.6 RC5 only. I am not sure that this will work fine also for v1.6 ST. :
Sincerely,
Masino Sinaga