I just ran a test from BC-HCE to Export a Utility Network to LandXML. Here is the LandXML that was created. It seems to work OK for me. I selected the Pipe and Node objects from the Graphics View (Window Select), but you can also select the Pipes and Nodes that you want to export from the project Explorer.
The main challenges with Export of Utilities are that Pipes, Box Culverts, Manholes, Box Structures are relatively straight forward to export as solids, but when you get to Pipe Fittings and Custom Shapes (Arch Pipes, Flow Channels and Objects represented as Blocks such as Fittings and Headwalls etc. they cannot easily be transferred using LandXML format because it really doesn't support Solid Objects or Blocks at all (so you can transfer names and attributes and then rely on the receiving software to assign what they want to use to represent the objects). And because while they are defined using Blocks in BC-HCE, once created in BC-HCE as a Utility Node they cannot be exported to AutoCAD DWG as Blocks - the AutoCAD export comprises Point and Line Objects primarily.
I would agree that an IFC type export (Shaded Solids with Attributes) or as solids to AutoCAD DWG format would be better however LandXML is what we have available today and that will round trip the data. When you import this LandXML back into BC-HCE the Fittings (Valves, Ts, Bends etc are created as Undefined Site Improvements and those are represented as a Square Box) - you can select those and add a Site Improvement to them so that they take on the form of the correct Utility Node.
In order to get data into Navisworks (and I am not 100% sure on what data formats it can read - I will look into that - you may need to read the data into e.g. Civil 3D and get it as you need and then export to Navis or save a DWG that has the solids in it and then open that in Navis.
I will feed this back into development