The concept reminds me of reality in the Netherlands (where I live).
My set-top box (cable modem, on copper but not a telephone line) features a double access point. One for my private network, one to be used as a wifi hotspot by fellow customers of Ziggo.
As long as I leave it enabled, I'm allowed access to their hotspots.
This public part won't interfere with my bandwidth, but it does add (a tiny amount) to my electricity bill.
So far, I have enjoyed the benefit and not felt a burden.