Mickle is right; bikes, like just about everything else, are built in general bike factories not factories specific to the brand, except for the big names like Spesh, Trek, Cannondale etc. who probably do own their own facilities.
Last year I visited a TV factory in Hungary; it's a massive facility that assembles TVs to the spec required by the brand manager, a much more efficient way than building your own factory. They built TVs for four major brands and when I asked the factory manager which he would choose he told me Samsung were specced with the best components but otherwise they are all the same.