Yes, but if they refuse the install they have to pay compensation and they really don't want to have to do that, plus do you really want to cancel the engineers appointment and your broadband just because they don't have a socket available?
Sky TV is provided in much the same way - just a cable.
If you don't like it, they will install a socket, but it'll be classified as low priority.
Can we see the other end of the cable though - need to see if they have installed an appropriate isolator.