Normally a journeyman plumber is a licensed plumber. You may be thinking of an apprentice plumber.
Some places call them master plumbers.
Here in Washington State, there is a residential license and a commercial license for a journeyman plumber.
An estimate can be given by anyone. That's sales. I know plenty of places that hire salesmen to keep the plumbers busy with work. Your rough in crews normally have a journeyman on site all the time, making sure the layout is correct.