In fact thatThat really depends on your electrical infrastructure. In a usual household, your neighbours cannot be on the same electrical source so you are 'safe'. Powerline cannot extend beyond the cupboard. In reality however, it is very common that electricity is leaking to your neighbours. In each situation you want to encrypt your home plugpowerline network.
We concluded that you really want security because if you have a cupboard for yourself, it will always leak. With company data, you want it secure.
There are a few ways to do that. A very simple way is to buy a set of powerlinespowerline adapters with management software. In that case you can only add a new powerline adapter with a password.