So, I know many people inside Duke and Progress, and here's the inside skinny:

Johnson was CEO for 30 minutes after the merger. Why? Because Duke didn't have confidence in him as CEO after a report came out that he made the call on a shortcut on a nuclear plant construction job. For this job, they had to cut a hole in the side of the containment dome. There's the right way to do it (you pay people who know how to do this a lot of money to do it right), and there's a wrong way to do it (you screw up the steel bands running through the containment dome concrete). Johnson made the call that dorked the containment dome, costing Progress billions of $ and taking the reactor down for a long time.

When the report came out, senior folks in Duke realized they didn't need Johnson at the helm, so they called the previous Duke CEO (Rogers) and asked him if he would come back. He agreed, and at the first board meeting of the merged company, they voted Johnson out and brought back the old CEO.

(Another version of the story is that he's an authoritarian personality, a 'my way or the highway' decision maker that doesn't work well with Duke/Cinergy corporate culture... the truth is probably a blend of the two stories, since the latter supports the former).

So, basically, this guy is a screwup who lost his job... and suddenly, he's the right pick for TVA?

Wow, we are totally screwed.

Links:
Was Johnson Ouster due to Crystal River Bungling?
(link...)

How saving $15M ended up cost $2.5 Billion (very detailed article, including comments by whistleblowers, and interesting side note on Johnson conflict of interest in insurance board):
(link...)

The Los Angeles Times estimates Johnson will walk away with $44 million from his one day of work for Duke.

So the guy has a history of screwing up Nuke installations and lying about it. TVA is a perfect fit, don't you think?