They CAN make a case by case assessment precisely because they are power aggregators.
No utility ever wants to pay more for power; especially when they are currently exploiting a loophole to get a buy/sell spread far in excess of what the regulators would ever approve for large contracts. I don't care what they told you, their motive was to protect their profits, not to save the ratepayers money. All this does is to ensure that people who invest in grid tied solar for their homes or farms are paid what they power they contribute to the grid is worth. When that happens the payback time for solar plummets. If there are associated costs due to grid issues those costs can be assessed and will be addressed when the power purchase agreements are negotiated.