I doubt EMR are going to pay out any extra money to hire in trains from spot hire companies.
Or to pay for extra trains to be leased, or to pay for training staff on them, or pay for overtime to cover people whilst they are released from their normal duties for training on them.
No doubt they are collecting penalty payments from Hitachi, and probably just want to hold on tight and keep collecting until their contract comes to an end and GBR take over. This could be a reason it's taken so long before an emergency timetable has been put in place.
The service is dire, there's been a tragic but unrelated accident, and no amount of money shelled out will improve the public perception of EMR enough in the short time it has left. It's not as though it's a suffering brand that given investment will grow in the long term - it has the clock ticking on it, and isn't worth the outlay.
I doubt DfT want to give any money to EMR to hire in extra trains, spot hire or leased. Politically, swooping in as GBR in a year or two will naturally align with the 810 reliability improvement curve. They hope! "Look how much better the trains are now!"
I'm sure British Rail was run down before privatisation in similar fashion, funnily enough!