On the UHF frequencies I seem to be able to tune my parents TV into Sky News, which is a satellite and cable only channel. The reception’s not perfect but its still there, how so?
Sky News is also on Digital Freeview.
However, what you’re probably picking up is a inadvertent broadcast emitting from a neighbour’s satellite decoder. I used to get this all the time, but only when I had my video recorder on. Very strange and very snowy reception, but a choice of a number of channels that definitely weren’t terrestrial.
I think it’s the same principle that allows TV detector vans to view what you’re watching.
There are a number of possibilities, depending on your antenna setup. For example, it is often possible to pick up a watchable signal from a nearby cable that is not even in your house or apartment. Equally, if you have cable or a shared antenna, one of your neighbours may be back-feeding Sky News into the cable from a satellite receiver, as a by-product of distributing the signal around his own home.
It is probably a local TV station; we have one here called SoTV (Southampton TV) which fills in what would otherwise be dead airtime with sky news, sports or QVC.
I think Mangetout has hit it on the head although I had previously thought of the other mentioned possibilities. My parents have a brand new TV that seems to give better reception than the previous set. It picks up the TV station from Londonderry, Channel 9, that does appear to fill dead time with Sky News. It fills airtime with mobile phone messages and music requests along with a view of the city at night so I’ll probably view it only when their own programmes aren’t transmitting 
Cheers, Pushkin.