I suspect it won't.
The previous attempt to electrify the MML came with a detailed economic case showing a hugely positive Benefit/Cost Ratio (BCR). But that BCR compared fully electric against fully diesel, and ignored the possibility of bimodes.
This time around, they have chosen not to publish any BCR figures, which makes me suspect that the financial case is bad and that the BCR is less than 1. There's no way that allowing 810s to run pan up instead of pan down gives benefits worth a billion quid.
Remember that MML electrification was promised as a political gesture to the north for cutting HS2 to Leeds and replacing it with the IRP.
More reliable railway (far fewer train failures, less track damage)
Lower cost of operation (big difference in fuel and maintenance costs)
Much simpler maintenance allows better early/late service / better service recovery / fewer trainsets (but not all at the same time)
Normally better acceleration means more attractive journey times
Clean/quiet/smooth journeys compared to diesel
More seats per train
Much of this is cost saving (fewer trainsets, staff etc) but that enables other benefits within the same budget...
Bimodes shift the equation but there is still a business case for increasing electric running...
I would set our expectations a bit lower in terms of doubling up in light of how many of the 33 units will need to be in service - as I and others have said before, the original intention requiring 31 of the 33 being in service is unsustainable. And in any case, we’ve seen so many letdowns in EMR’s life that I’ve set my expectations low.
Let’s assume that some peak services will be doubled up. If in reality it does end up being “most” (I’m not saying “most” won’t happen, I’m just urging caution), then we would see that as a pleasant bonus.
Have Hitachi ever met their contractual commitment for trainsets yet?
GWR run short formed even after stripping back their timetable; LNER had to retain an entire trainfleet to cover lack of availability.
The availability committed in the contract was heroic for an EMU, let alone a complex bi-mode with numerous issues.