That is pretty impressive.
The best I've seen is 49Mbps, on the same circuit, all other breakers turned off. Since it isn't using the ground, the ground wire shouldn't matter, but the rest of my wiring and electrical devices (outlets, switches) are all pretty good and just plain breakers, no GFCI/AFCI on there (well, on that circuit and the rest off shouldn't matter).
Anyway, its a 1961 house with 12/14 gauge wiring through most, but undersized 16/18 gauge grounds, except for the rewiring I have done or one or two former owners, where it is all standard 12/14 2/3 wire with full sized ground Romex.
Anyway, that was the best. I think the best, split phase connection I saw around 20Mbps or so, and most of my same phase connections where in the 30Mbps range. The worst I saw was about 15Mbps on complete opposite ends of the house and across phases. I was actually mildly impressed by the worst performing one and the best peforming actually would work pretty well for a lot of stuff.
But not as good as even Cat5 and fast ethernet, or wireless. Well...if I had to beam wireless across my house, it would be better than wireless. With 5e and soon to be 5e or 6 through my house, no need for the powerline and the worst wireless performance I have within my house is around 50Mbps and typical is more like 60-100Mbps with around 150-180Mbps in my dinning room and playroom/familyroom.