SELECT tstzrange('-infinity','infinity') && tstzrange(NULL, NULL);
 ?column?
----------
 t

SELECT tstzrange('2013-01-01 00:00:00+01', '2013-02-01 00:00:00+01')
    && tstzrange(NULL, '2013-03-01 00:00:00+01');
 ?column?
----------
 t

SELECT tstzrange('2013-01-01 00:00:00+01', '2013-02-01 00:00:00+01')
    && tstzrange('-infinity', '2013-03-01 00:00:00+01');
 ?column?
----------
 t

SELECT tstzrange('-infinity','infinity') = tstzrange(NULL, NULL);