The DfT sign-off on any rolling stock changes at XC and Arriva gets paid a management fee for XC for following the DfT's orders.
Grand Central's first concern will be their track access agreement expiring in December 2026. Once they've got an extension they can look into new stock.
Bradford only has ~30 miles off wires and Sunderland ~40 miles. Both could be done roundtrip by a battery EMU so a battery 397 would be a possibility.
Arriva won't avoid signing a deal for Grand Central on chance DfT want them them for CrossCountry at a later point. A deal with Grand Central until December 2026 would be better for Rosco than having units in storage. Grand Central seem to have a choice between ditching the 180s and having a very unreliable fleet for next 40 months.