I have been informed by a Ford dealer that all the Mild Hybrid 1.0 Ecoboost engines now have a timing chain as opposed to  a wet belt running in oil.

An independent dealer however, says they have only done half a job, as the oil pump belt still runs in oil and will be subject to degradation with the same damaging result.

Any more definitive info on this please?

The independent dealer is correct.  Chain for timing.  Wetbelt for oil pump.

The oil pump wetbelt still has a recommended replacement interval of 10 years.

It is worth noting that so far we haven't seen many oil pump belts fail on chain engines.  There is also physically less belt material that can clog up the oil pump.  And as long as the engine is shutoff immediately on seeing the oil light, the engine itself may still be serviceable if the oil pump belt fails, unlike if a timing belt fails where valves will hit pistons.

Is there any car age or mileage before which belt degradation of the belt material does not occur?

The major job takes 8 hours, how long would it take to repair likely damage after an oil pump belt failure on a timing chain model, where the pistons and valves didn't smash?

The belt can be wrecked quickly by using the wrong oil or adding engine flush during a service.  Short drives on a cold engine also accelerates degradation of the belt.  As does leaving the car parked unused for several days at a time.

On a car that does motorway mileage every day, fully warmed engine, oil change every 12 months, the belt will likely still be good at 80k+.  

If the engine is switched off immediately when belt failure is noticed then there would not be any additional damage caused.  Just needs the belt replaced as if it was a routine belt change.  If it isn't switched off immediately then oil starvation will cause damage ranging from turbo and vacuum pump to shaft bearings and bore damage.