How can resource mailbox migration be addressed so that users are able to collaborate and book resources in both source and target domains.
Resource mailboxes are normally grouped in a separate collection. On the Properties of this collection - Members Tab - "This collection includes resource mailboxes" checkmark needs to be selected. This enables Calendar Agent to process calendar synchronization in two directions: source to the target and target to source. This way all the booking that happened on either side will be available for switched and not yet switched users providing full collaboration during the coexistence period.