Here in Ohio, a technician must be certified prior to working unsupervised. You can check out the training/test/certification at
www.wildohio.org.I don't feel that the training and test they take is actually enough to make me feel comfortable turning a tech loose to fully represent my company, but it is a legal requirement.
I have had a number of employees and each one has been different. Most I felt comfortable going on their own (for pickups and such) in a relatively short period of time. Others not so much.
What I guess I'm getting at is that each individual will be different. I don't think you can quantify when someone is ready with a check list.
To use an analogy, I have four children, each will be able to legally drive at 16. I am quite sure that I will have a different comfort level with each of them based on their personality, level of responsibility, and how they are influenced by their friends and peers. My oldest is most likely to tell someone to go pound sand if they try to get her to do something she shouldn't. My second oldest might think about it but will probably say no politely. My third would walk away looking like he was gonna call the cops on them. The youngest, I might have to make sure I have bail money ready!!!