Actually, I think you mean Sacramento Municipal Utility District (SMUD). One of the issues is that some publics are "FERC-Non jurisdictional" which makes it difficult for FERC to direct them to do things. However, in the price caps FERC did regulate many of these folks. I also think that some of your numbers may be a bit off the mark.
Freerepublic article on who the ISO said gouged California and by how much
If you look at the above article, BC Hydro was just small change compared to Duke, Williams, Reliant, and Dynergy power traders.
From what I know about the Bonneville Power Administration almost all of the power they provided to California was in the form of energy exchanges. That is, BPA supplied power during the peak hours of the day to keep black outs from happening and Cal returned the energy plus and increment to represent the lower value of energy at night during off peak hours. The last I talked to some folks at BPA they still hadn't been paid for some of the power they had shipped to CA over a year ago. That was actually one of the stated reasons BPA raised its wholesale power rates to NW customers last October.
Therefore, I don't think public power can be used as an explaination for why the Oregon PUC and the Washington UTC are recommending to FERC against refunds.
M.D.- If you're defining 'biggest offenders' as the ones who charged the most $$ per kilowatt hour than I agree with the statement above. If biggest offender means who charged the most ovewr time than I would agree with Robert.