I think the transfer speed would depend more in the quality of the lines, the amount of interference, distance of the run (I'm no electrician, but whatever the equivalent of attenuation might be), whether it passes between circuits, etc. I doubt you'll ever see 500Mbps transfers on a 500Mbps powerline, but I hope it is sufficient for your needs. If not, it might be worth just running some CAT6 or high quality CAT5e.