I had and experimented with at the few places I found, home routers outside peoples houses and also the odd business downtown, home routers show BT fon as the wifi name.
Never had much luck, sometimes was good and other times just wont go, If it did then dial up speeds would have beeb better.
I use the BT email and password I think.
I got my HH3 router giving out the personal WIFI of DanielsBThub ( changed the name to that) and also 2 others noticed had a bit of a name change to BTWiFi-with-FON
Tried getting on my own BTfon by logging in liek I would out and about on someone elses.
Never was anygood, sometimes did, othertimes not.
Moaned about this to the BT bloke that came to sort out phone line this year, he says they can use to get computer on the customers internet but not that good, coming from BT bloke says it all.
Why I keep my HH£ doing this when can opt out, might be good one day if on holiday on a duff 3g place for phone so might find BT hotspot, me things not anygood.
I would noyt rely on it. Always a dissapointment downtown when trying.
Mostly does not log in and give internet connectivity past the landing page, Good then!.