Yes, assets can be moved from one site to another by system admins by using the Asset Importing and Exporting feature.
Steps to move assets to another site:
- Export the Assets
- On the exported excel sheet update the Site Name & Site ID columns
- Import the saved sheet in the Assets tab
- To change the site of the asset update the Site Name & Site ID columns in the exported field column and then import it.
This way, the assets site will be changed and no duplicate will be created.