Ionut,
The .3WS file format cannot be natively read by ArcScene. Keep in mind that you should be able to render the City Engine Web Scene in any WebGL compatible browser without the need for a plug-in or a client install of CityEngine. However, my suggestion going forward would be to subset the 3D content present within the scene to write a number of .3WS files of smaller total size. While the recommendation is to keep the file size limited to 50MB, files larger than this should render depending upon the complexity of the content within the scene. If you are planning on sharing this with users one option would be to create a 3D layer package using ArcScene. Users with whom you are sharing this data will need either ArcScene or ArcGlobe to consume the layer package. Another option would be to share each of the Visibility outputs as a feature service or tile service if they are output raster datasets to ArcGIS Online and then create an AGOL Scene that can be shared with other ArcGIS Online users of your choosing. Keep in mind that this will cost credits and will take more data preparation time than the .3WS would. In addition, Multipatches are not supported as of yet within the Scene viewer. Hope this helps!
ArcGIS Help (10.2, 10.2.1, and 10.2.2)
http://www.arcgis.com/home/item.html?id=38fede3935a440e49cf316dcae6aae47
