Hi,
I've been talking to Renato and other Esri staff offline, and wanted to add some information.
1. As you know, we do not provide access to the fine-grained network topology on the client. We've developed a detailed and flexible set of tracing configuration options to address the most common workflows, but we're no under no illusions that we've got them all covered.
2. You can use the Export Subnetwork geoprocessing tool to return the network connectivity for a subnetwork. Depending on the workflows you are trying to accomplish, this might help.
3. Our documentation hints that this capability is available with Trace. As Renato pointed out, this hasn't been implemented yet. In the short term we're in the process of removing this from the doc, but it remains on our long-term roadmap.
4. Starting with ArcGIS Enterprise 10.8.1, the Enterprise SDK will allow access to utility network topology in a Server Object Extension (SOE). You'll also need a way to call this SOE, either via directly calling a REST endpoint, or by writing a Server Object Interceptor (SOI).
I hope this helps some.
--Rich
P.S. If you have more specific information about the business cases you are trying to solve we can investigate whether we could add the necessary options to our core product.
Here are some ideas for the cases you described above.
* You should be able to use the Nearest Neighbor filter to return the two nearest devices of a particular type. (You might need a second trace to find the nearest device so that you know the order of the devices.)
* You might be able to use Functions to find voltage drop along a downstream path