The contacts are disconnected. Each domain name (domain object) has one connected registrant, known as a contact object. The contact object comprises various contact information concerning the registrant and has an identifier in the system, known as a contact-ID. In conjunction with a change of registrar (transfer), the domain object is relocated to the receiving registrar who manages the domain object and the contact object for the registrant. This means that the registrar can administer domain objects and contact objects via EPP. In other words, other contact objects can be connected to the domain name, for example, a technical contact.
For the registrant, an entirely new contact object is created (contact ID) that includes information on the registrant. As a registrar, if you connect other contacts to a domain object on behalf of the registrant, you can opt to use an existing contact object that you are managing, or create a new one.