A reliable 'source' has informed me that the B737 was actually holding at Sierra 2 (the CATII/III hold) and not at Tango 1 as I depicted in my original diagram (since updated). So, we can deduce that the B737 was NOT at the T1 holding point which would have allowed enough clearance for the B767 to pass behind.
Not sure which type of B767 was involved but I know that the wingtips of the B767-300 are NOT visible at all from the flight deck.