Comcast in the US (idk ++millions of users) by default enables a 2nd WiFi network that is open to all of their subscribers. Is convenient, amusing, and annoying, depending on perspective.
Back when I was a Comcast customer I did find it useful when I was in an area with no - or too slow - mobile-data connections.
I assume that traffic on that network is always qossed to lowest priority, but I've never used it (I don't use a BT router)
They never disabled my account - I not get worldwide FON roaming for free forever - yay!