Could only see the start of the video -- it was loading too slowly today. There has been a Canadian 48 horse Percheron hitch pulling a cultivator, in Alberta I think. They did actual work, not just a short pull. Some video is on youtube. There was also the Famous Fifty Clydesdale hitch of Navan, Ontario. All hitched to 1 wagon! This went on the village streets and around corners, I believe. Two horses in the lead from the Experimental Farm, and then 4 abreast for the rest of the hitch.
As to how many lines ... That would vary. I've driven 4 abreast with 2 lines. Show hitches are set up differently, as are competition driving teams.
That would be crazy!! One of my favourite classes at the Royal is the 6 horse hitch and I always watch it every year. It is so impressive and I love watching them go around the ring. I have seen a couple of misshaps though and I would be terrified driving 48 of them in case something happens...