It's unlikely that it's written off, I've seen trains with a hell of a lot more damage go back into service. I suspect it will just require a new front end on it, although it depends how bad the damage is further back and how it's built. With many trains, for example the HSTs, Eurostars and 58s, the cab can be swapped over, and spair cabs are available (spair Eurostar cabs can be seen at North Pole Depot), and with a lot of other types it would just be a case of swapping the fibreglass moulding from the front. With trains that new, I'd have thought they'd have body parts in stock, or else one could be made up quite easily. The front ends on the 444s are identical to the 450s (and 350s) AFAIK. Were the damage just to the windows it's possible that they could use it with the cab inside another train, and I'm sure that sort of thing has been done before, but not with that much damage. Would anyone want to drive a car with that much damage, even if it was the back or side?
Out of interest, are the fronts on the Desiros fibreglass or are they Aluminium? The body looks dented, wheras fibreglass will crack. If it is aluminium it should be possible to knock the dents out, or even run it as it is (one the windscreens, corridor connection, lights etc are repaired).