"Estimated date of dispatch of invitations to tender or to participate to selected candidates"
So this is just an expression of interest stage. They are aiming to deliver the actual invitation to tender to interested builders on 26th October, not announce a winner.
Yes, the actual ITT (invitation to tender) should be this week (26 October)
ITTs will usually give the bid spec : minimum first batch size, number of cars, capacity, max speed, type of fuel, delivery date range etc
Very likely to be electric, with diesel generator that can be replaced by batteries in mid to late 2030s (later batches battery electric). Personally I would like to see minimum 3 cars per unit.
For quick reference,
I think Northern is ultimately looking to replace :
Class 150. 78 units, 162 vehicles
Class 155. 7 units, 14 vehicles
Class 156. 65 units, 130 vehicles
Class 158. 53 units, 114 vehicles
Class 170. 16 units, 48 vehicles (not sure if these are staying)
Class 319. 12 units, 48 vehicles
Class 323. 17 units, 51 vehicles (more expected from Midlands)
Class 333. 16 units, 64 vehicles (not sure if these staying)
Class 769. 8 units, 32 vehicles
So probably minimum of 400 vehicles, perhaps nearer 900 vehicles under options