article in boston hearld indicates taxiway Z is not illuminated with blue lights, though it does have green centerline lights...somehow this is OK by regs. banking right from base to final if the copilot caught sight of the HIRL and thought, well there is the left side of the runway, can't see the right side of the runway, somewhere down here...kind of thing
while yes, the pilots made a mistake and got lucky that no one was hurt, we must re think markings and lights as menitioned before.
it is amazing things like this don't happen more often.