I agree that given the current environment, it would require regulatory changes to implement the data ownership concept. And given the degree of regulatory capture in such markets, good luck getting such a change implemented.
The main things that seem likely are: 1) consumers will be guaranteed some sort of free access to their own usage data, partly in hopes that increased information about one's power usage will encourage people to use less; 2) there will be some sort of restriction on how personally identifiable, non-aggregate data can be used, e.g. the power company won't be allowed to infer things about your lifestyle based on power usage patterns, and then sell that data to advertisers.
Tricky areas are what counts as "aggregate" data (there are a lot of potential pitfalls there, both intentional exploitation of loopholes, and accidental leakage of identifiable data into aggregate data), and if there should be some sort of distinction between internal-to-operations and external data mining. For example, perhaps it would be okay for power companies to infer more specific things about individual lifestyles, if that information is only being used to optimize the power grid.