Of the many Zetec powered cars that I have seen towed in with broken timing belts, I have never seen one with engine damage caused by the broken timing belt.
On the other hand, similar Volvo and VW engines with a broken timing belt almost always had bent valves.
Install the belt and see how the engine runs and go from there. Assuming the worst just because the timing belt broke is either ineptitude or dishonest. In either case, that is not someone I would want working on my car.
