You do realise the 387s on the GN aren’t fitted with ETCS?I think it is more a case of the Treasury having a stranglehold over DfT expenditure rather than sense.
I have seen mentions elsewhere of if GN were to take the 379s on, they would need ETCS fitted as KGX-PBO is the first NR main line route to transition to a "signal less" railway. If this is true then someone will need to stump up a few million in installation costs - idea while they are sitting around in warm store.
Again. if this is true the DfT could be playing Russian roulette with the Rosco to see who will cave in and sign off the investment. While they are parked up they are costing money rather than earning, and maybe DfT think the Rosco will fit the ETCS equipment to get the trains earning again. On the other hand perhaps the Rosco will hold their nerve and wait for DfT to crumble. The other option of course is to either fit the 379s with 750V DC or switch around another fleet.
I am guessing there are storage sidings now available which the 365s vacated.