Shunting does vary depending on who you work for and even depot’s of the same company.
At our place none of the three of us had class 1 licences, I have mine now anyway and don’t shunt very often now anyway.
One has a car licence only the other has C1 and PSV but nothing else and the newest shunter not even sure he even has a car licence as he usually comes on a push bike.
Yet another one of our depots to be a shunter you have to have a full Class 1 licence, but I believe they have to go out on the road at times and I believe there is public access through the site.
But all shunters are trained on the tug and signed off, so I guess in effect as a tug is classed as plant in house training would suffice as long as it’s private ground.