This is surely the important point; the relevant question is "what is the cost of replacement versus the cost of repair?". (Note that this is arguably an oversimplification, as you want to amortize them over their remaining lifespan, and often the new option will have a longer lifespan.)
The cost of the vehicles is near scrap value (and the value of the destroyed vehicles will be near the same); to replace them you have the cost of getting some FoC to haul the replacement to Wabtec, to repair them you somehow have to get the destroyed vehicles to Wabtec which will near certainly be more expensive; then you have the cost of doing another refurb versus repairing, this is a more complicated question but I would be very unsurprised if doing another refurb was cheaper.
That said, depending on what TS foresees happening to the HSTs, the expected delivery date of a replacement set, and how quickly they get replaced under the new electrification scheme I wouldn't be totally unsurprised if no HST was procured to replace it.