Now that I think about magic as an option I'm fairly sure it can't be magic because how would the non-unicorns use the things such a fans, lights and sewing machines. Unless of course they have some kind of magical power plant filled with unicorns.
It also seems that even the simplest magic is very hard for them. since Twilight is skilled in magic it's self, and still has truble doing most things.
But another thing I just thought about is that maybe there machines are all clockwork and run off springs, gears and pony power like the snow plows in "Winter wrap up"