I didn't see a date on this article but it appears to be old.
3 mb/sec.?
My DSL connection push's 20 mb/sec.
I played with PowerLine Networking in the mid 90’s. Those were the typical advertised speeds at the time. I see a “2004” watermark in one of the illustrations so I suspect this “how-to” is at least 10 years old.
That was (and apparently continues to be) the problem with BPL - pathetically slow.