Here in the UK I hadn’t heard of a locomotive builder without rail access. Sounds odd in a nation with a dense rail network and many potential sites for a factory, and awkward for getting steel in too. But maybe it wasn’t standard gauge and was being dragged to a point where it could be loaded onto a ship for export? One of the Glasgow or Manchester manufacturers perhaps? The restricted loading gauge over here would preclude transport on a flatcar even with cab, chimney, etc removed. Or perhaps an export product that was seriously out of gauge for the UK?
I have seen a photo of horse teams moving subway cars by road from the nearest rail yard to Golders Green depot on the Northern Line in London a century or more ago. Back then the deep tube lines were self-contained (they are connected now). It did look odd to see electric stock pulled by animal power.