I am pretty sure Engineering Consulting firms performing work for the Departments of Transportation (DOTs) in all 50 states are either using Infraworks, OpenRoads Conceptstation, or both for Conceptualizing projects and Visualizations for Stakeholder and Public Engagement. Also, within those State DOTs there are several engineers who use those tools internally as well … not just the consultants.
Bentley is developing an iTwin for Unreal plugin, but I think only a fraction of engineers would be willing or interested in making the leap into Unreal due to its complexity. The rest would probably adopt Twinmotion due to its simplicity.
AutoDesk has a Revit for Cesium plugin that can be used to stream Revit models into Unreal from a Cesium Ion account, but I have not seen any plugins for Infraworks.