There is a method you can use to share the building between your two user groups. I've detailed it below:
1. Add orignal account (account 1) as a contact by clicking "manage" and then "contacts" in the top toolbar
2. Open property in question
3. Share property with account 1
1. View buildings in List view
2. Shared building should be visible as belonging to account 2.
3. Duplicate shared building
4. Rename if appropriate.
Is there a way to transfer a building between accounts (once its finished)?