Ultimately both governments and private entities can run things efficiently. And both governments and private entities can run things badly. The UK government has an excellent recent record of running rail franchises when it has had to step in and bail out franchises (it ran it profitably, and with excellent customer feedback on service), so it's a good bet that it'll do better than the existing providers for the time being.

It is the same people who worked for the franchises working under government control - it is the senior management who go but the actual doers are the same.

Incentives on one is to maximize profits, which in a monopoly means just extracting more money and spending less.

Incentives on the other is electability (or ideology, perhaps rare), which at least has the possibility of meaning doing a good job.