[user104658]

It's one account per household so they definitely can track it (or at least suspect it) if there's regularly more than one person on the account from wildly different locations, for example, my father in law used our Netflix account for a while when he was deciding whether or not he wanted it, and they live over 250 miles from us. He eventually got his own account anyway (as part of the fairly recent Sky package deal, I think) but... that would have been fairly easy to identify as multi-account-use.

If everyone using it lives fairly close together (i.e. same town) it'll be impossible to enforce, as there's no way to prove that the IP addresses logged aren't legitimate locations for the household members.