It may be easier to document than I thought.

Anjali Sheffrin's July report shows data for June (p. 5).  The majority of real time purchases are from CERS/DWR and the price for OOM is substantially higher than other R/T power.  The need for OOM greatly diminished begining in late May, yet CAISO bought most of its R/T power from CERS/DWR.