You can move interaction references, resize them, and generally manipulate them freely. When you cause the symbol to overlap an object lifeline, it attaches to it automatically, and this attachment is represented by a small bump on the top edge of the symbol where it meets the lifeline. If you drag or resize the symbol away from a lifeline, it detaches automatically.
If you move an object that is attached to an interaction, the symbol resizes itself automatically to remain attached to the object lifeline.
You can manually control whether object lifelines are attached to an interaction reference that passes over them by clicking the attachment point.
Note that an interaction reference cannot be copied or re-used in another diagram. However, multiple references to the same diagram can be created.