I'll take a punt here and suggest that your car is the turbo-diesel variant with the six-speed dual-clutch transmission. The dual-clutch unit is vastly more problematic than a conventional automatic transmission and has given many manufacturers (Ford and VW being two of the main ones) all sorts of consumer grief over the years.

The unit in your car is a wet-clutch design which is much more robust than the cheaper-to-make dry-clutch type, but has still been known to fail. (The dry-clutch units on Ford's Focus, Fiesta and Ecosport models cost Ford millions in fines when they began failing at low mileages and the ACCC stepped in.) That said, the wet-clutch units have also experienced problems, but before you scrap the car or shell out $15,000 for a new gearbox (which sounds like an ambit claim in the first place) have it checked out by a specialist. In many cases, jerky progress like you're experiencing can be caused by the transmission's control module or even a faulty speed sensor inside the unit, rather than the actual transmission hardware. If that's the case, it may be more economical to repair the car.

Beyond that, I totally agree that less than 100,000km is not an acceptable lifespan for a major component such as a car's transmission.

The PowerShift transmission problems related to the dry clutch transmission fitted to the Focus, Fiesta and EcoSport models. The Mondeo has a wet clutch transmission, and as such, is not affected.

To have a transmission fail after just 100,000 km is not acceptable, particularly when it hasn't been used for towing. I assume it's a dual-clutch automatic, which has been troublesome in many Fords around that time. Ford should be showing some interest in fixing it for you; at the very least they should be offering you part compensation for a replacement transmission. If you can't get any help from Ford's customer service people, go to the Victorian government's consumer affairs department, or think about going to VCAT.