The information in this article is specific to the Source as Exchange or Office 365, and the Destination as Exchange or Office 365.
We handle resource mailboxes the same way that we handle regular user mailboxes.
If you can log in to the resource mailbox using a web client (i.e., Outlook Web Access), we should be able to log in as well, and migrate the data. If there is no way to log in to the resource mailbox using a web client (like OWA), then we also cannot log in and migrate the data.
In some cases, the resource mailbox is just a shared calendar that is owned by a user. For those cases, when the user's mailbox is migrated, we should be able to migrate the resource mailbox calendar as one of the user's calendars. Once the migration is complete, you could set sharing/permissions on the calendar so that it can be accessed by other users.