Has nothing to do with the trailers, they are still 4, 5, 6, 7 or 9 wire systems depending on what type of application they are used for, but they have changed how the electrical signal is sent to that trailer from the tow vehicle and like GA said, many of them are fully network capable to route that electrical signal to different areas for different functions.
Motor vehicles are no longer dumb terminals, they take an active roll in their management, I saw a brand new truck at my buddies yesterday and came from the factory with brake controller fully integrated in the dash that self adjusts something like a 1000 times a minute to adjust brake bias on the trailers electric brakes.