It's random, I've had plays were I was constantly caught, I had others were I was justifying CBs left and right and my infamy was super low. Your government type will have a great effect on this, as certain reforms can increase justification time to 300+ days, while fascist dictator ship is around 70-80 days I believe. Which means that even when you get caught 20 days in as fascist dictator, you are already 25% done and take 25% less infamy.
Also for those that like to cheat, you can justify for 0 infamy by saving around every 10% completion of a CB and then reloading when you get caught. That way you can make it all the way to 100% without taking infamy. Not gonna argue about using this here or not, but it's a possibility, in single player games at least.