Using email to notify users and admins assigned to tickets is straightforward and there's no real need to go into detail here. In this system, I have one admin receive a notice when a new ticket is created. This admin is in charge of assigning the ticket to the appropriate admin user. There is a rule that is run when a ticket is updated and on the condition that the ticket was assigned to one person and is now assigned (after the save) to another person. If that condition is true, an email notice is sent to the new assigned person. A similar task shown in the RULE below illustrates how the one assigned receives emails when the ticket gets commented on by the user.
Notice that the last condition makes certain that the admin assigned to the ticket does not get an email notice regarding his own comment to a ticket.