CSOM Project Summary Task

How do you access the Project Summary Task via the CSOM?  In the PSI it is in the Project dataset under TASK_ID 0.  In OData it is simply integrated in the Project class as ProjectDuration, ProjectActualCost, etc.

In CSOM the PublishedProject doesn't contain these fields and there is no Task in the Tasks collection that has the rollups.

Is PublishedProject.SummaryTaskId somehow involved?  I attempted to load that task via:

var summaryTask = _projContext.LoadQuery(proj.Tasks.Where(a => a.Id == proj.SummaryTaskId)).FirstOrDefault();

But that is throwing a "The data is not available." exception.

Thanks,
Mike