DTrack supports two different coordinate outputs, one is called 'Powerwall' and the other is 'Standard'. If you select 'Powerwall' than the right-to-left conversion will work:
Code:
# VRPN Tracker connection (to ART Dtrack)
vrpn = viz.add('vrpn7.dle')
headtracker = vrpn.addTracker('DTrack@localhost') #Default sensor is 0. Head tracker is on DTrack sensor 0
headtracker.swapPos([1,2,-3])
headtracker.swapQuat([-1,-2,3,4])