We have a custom script that looks up a requester in our own system when they send in a ticket. We use this to update the ticket with customized priority, subject line, tags etc based on their account in our system.
One thing we do is add the requester's account manager if they have one. However, our script doesn't fire until the ticket is already created. So, adding the collaborator alone doesn't actually notify the collaborator--they won't know about the ticket until there's another public comment posted.
One thing I could do is pass in a tag when the collaborator is added, which could activate a trigger to send another reply, but that would double-notify the requester. Also, since collaborators could be other external users that the requester cc'd in their initial email, I don't want them getting messages too.
Since the collaborators we add are all agents, would internal notes be sent to them? I was thinking we might be able to post an internal note when the account manager is added as a collaborator, but I don't know for sure if the notifications would work that way.