Additional Contact Messages and Responses visibility

Summary:

Our client is wanting to understand what visibility the additional contact on a SR would have, particular around messages to the Primary Point of Contact from the Agent.

Content (required):

I haven't been able to find an answer to the visibility restrictions on the an SR for the additional contact. If an employee was to raise a service request through email and CC another employee (who would become an additional contact on the SR), are both given visibility of messages and correspondences with the Agent on the SR?

Version (include the version you are using, if applicable):

HR Help Desk Redwood