Have posted something on how to do it on the official Oxygen forums:
OXYGEN>ADDON CONFIG & SCRIPTING>Named Properties
In O2 'Geometries' open the 'Named Properties Box', choose 'NEW', write in the first line 'map' as parameter and 'house in the second line as value. The model will appear on the map in a size, defined by your Geometry LOD. Your bridge assumed as building class.