Starting this year, the broker's distribution charges are made up of hourly "meter charges" based on total customer subscriptions, and weekly charges for broker contributions to demand peaks. Since demand peaks are global, not per-broker, you might ask how an individual broker might anticipate them. To address this, we have introduced a new DistributionReport message, sent to brokers in each timeslot, that gives total consumption and total production for the timeslot across the entire customer population. The net of consumption-production is the number used to compute demand peaks. As a result, brokers now have the same information the server uses for this purpose.
Since DistributionReports were not a feature prior to this year, anyone wishing to look at peak demand behavior in previous tournaments would have to compute net demand in each timeslot. I've written a logtool script that extracts that data you need to do that, which you are welcome to use. It's called ProductionConsumption.java, in the github powertac-tools repo under logtool-examples.