I have been following this thread with interest (accidental pun). Where I am (New Zealand) the term apartment doesn't mean anything in relationship to ownership either. It could be leased, owned, rented or whatever.
Edit: using everyone's favourite source the world apartment has different meaning in different regions - broadly the term 'flat' is a better fit with British (maybe even non-US?) readers, though with NZ being an exception, despite our usual English centric approach to language.
http://en.wikipedia.org/wiki/Apartment
Which does kind of make sense, considering they are in all other regards the exact same thing.