In ArcObjects you can get the service properties of a map layer by looking at its
IWorkspaceName.ConnectionProperties property set, even if the layer is currently invalid due to a broken connection.
Why are these properties not exposed through
Layer.serviceProperties dictionary if the layer's data source is broken?
Is this any different in 10.1 (I am using 10.0 SP5 at the moment)? Just tested at 10.1 SP1, it's the same story.
This ESRI forum post states that they are not exposed, but not the reason it was implemented this way or whether it is going to be improved.