What is evidence on relative efficiency of privatised vs governent run infrastructure?

Note: Already have some question a bit like this below

• Financial performance
• Setup vs running when existent (one thing to run postal system when set up but what about set up)
• "Political capture risk"
  • Point that bureaucracies get entrenched (basically they capture gov). e.g. french unions, greek unions and pensions
  • Does same thing happen with private companies (but they hide it better)