Granted, it's a modular system whereby they can probably replace the individual sections of track with new parts and simply drop them in - but they're pretty large pieces of reinforced concrete and it's been a long time since they've been purpose-built for the OBahn.
They are about to be purpose built once again for the O-Bahn extension, so it would make sense to keep on producing more of them if a track replacement program is coming up - even if it's just for the bits in acceleration and braking zones.
It's been interesting to note the switch from highly specialised rail equipment to road-rail adapted trucks with many of the recent projects. I'm sure there are some soon-to-be-unemployed engineers at Holden who would love to be paid to work out a solution applying the same principle of adapting otherwise standard equipment to work with the guideway.
Has the patent/proprietary technology been opened up yet, does anyone know?
The patent would definitely have expired by now. If the manufacturer were to demand royalties or a hefty price for handing over the plans, it would be legal to design a replacement by reverse-engineering.