Hello,
It seems strange that unlike AutoCAD, Revit, Navisworks, and most other Autodesk applications, InfraWorks does not reference it own models natively (aside from exporting to FBX)! Resulting in large sized models and often one person only can work in the model at a time (although BIM 360 addresses the multi team member collaboration issue slightly).
I think the ability to reference InfraWorks models in InfraWorks would make for reusable and smaller models with easier team authoring workflows.
Thanks,