The below code browses through the drainage and utilities model to get the links, nodes, reachs etc.

//Required references
using System.Collections.Generic;
using Bentley.CifNET.GeometryModel.SDK;
using Bentley.CifNET.SDK.Edit;
using Bentley.Civil.Subsurface.SDKNet;

 public void BrowseThroughDrainageAndUtilitiesModel()
        {
            //Get connection to current document
            ConsensusConnectionEdit con = ConsensusConnectionEdit.GetActive();

            //Get active geometric model
            GeometricModel sdkGeomModel = con.GetActiveGeometricModel();
            if (sdkGeomModel != null)
            {
                //Create subsurface model
                Bentley.Civil.Subsurface.SDKNet.SubsurfaceModel subSurfaceModel = Bentley.Civil.Subsurface.SDKNet.SubsurfaceModel.Create(sdkGeomModel);

                //Get all links
                IEnumerable<Bentley.Civil.Subsurface.SDKNet.Link> Links = subSurfaceModel.GetLinks();

                //Get all nodes
                IEnumerable<Bentley.Civil.Subsurface.SDKNet.Node> nodes = subSurfaceModel.GetNodes();

                //Get all reachs
                IEnumerable<Bentley.Civil.Subsurface.SDKNet.Reach> reachs = subSurfaceModel.GetReachs();
            }
        }