Will cable & internet pollute our power?

Have you not heard of grounding?

If power lines and the home circuits could carry radio frequencies why aren't our homes giant antennae nodes on enormous multistate grids ???
I guess dirt is a great dieletric ??

There is an enormous amount of garbage on ac lines, with some of it deliberately put there, some by the power companies. There are many devices intended to remove this garbage and some to remove the dc. I have tried over forty of these but have found most do more harm to your music than good. If you install it and let it break in and listen and after a time remove it and you sound improves, sell it. I have found only the Synergistic Research PowerCell stands out in greatly improving your sound.

Surge and power conditioning devices definitely filter out these frequencies so that you can't realy connect homeplugs onto the power conditioner or surge suppressor. I use the netgear powerline devices.