Even though Google's new Cape Town nodes are in limited production / test mode, users have been connecting to both the local data-centre, as well as to overseas datacentres [e.g. London?].
Presumably Google is still tuning the DNS based on usage while simultaneously expanding the datacentre capacity.
Interestingly it is only mail.google.com that returns a non-local host. So apparently mail is not amenable to normal caching modes or it would have been done through either the [presumed] GGCs or even transparently cached within the Cape Town datacentre.