How exactly in depth was the refurbishment? They received new seats yes, but were new PIS systems installed? New carpets? Overhauled traction equipment? I agree the Class 458/4s (if Porterbrook could lease them to Eversholt) would be good on Scotrail to bolster the Class 334s fleet if AC converted. Recently the intensively worked c2c Class 357s look dreadful inside, and a refurbishment is in dire need, seeing as they still bear National Express moquette and pole purple.
Unfortunately though, I think the latter prospect is more conceivable, The Class 458 was always a shambolic design which received too many modifications in its time to try and reverse their image. Quite frankly the Alstom Junipers were designed and built during a period of financial instability on Alstom's behalf. They were shoddily built and antiquated construction equipment was utilised at Washwood Heath with a lack of quality control from the French Design. I think the heavily corroded bodyshells of the Class 458/4s will be scrapped and useful parts will be cannibalised to refurbish and maintain good reliability of the well performing Class 334s.