Hi
there are different scenarios possible.
You may setup email notification as well as workflows.
The typical case is that a corresponding user exist in service desk. So the new message is created for the right user, even through creation via RFC from ECC backend.
In case of status change the user gets a mail notification and if necessary logon to solman to post a reply.
I assume you can also use the sap business workplace in ECC.
I am not sure about the licensing.
Regards, RP