Without including Liverpool to Nottingham, EMR timetable plans were based around having a fleet of 11 X 3 car 170s and 33 X 2 car 170s. With EMR now getting the 170s currently with TfW, that will leave them with a fleet of 13 x 3 car and 27 x 2 car, a shortfall of 4 units or 6 vehicles.
(Speculation) If EMR retain all of their 26 x 158s that leaves them with enough for 6 car operation* Liverpool-Nottingham (18 units), 4 to make up the shortage of 170s, and 4 spare.
* There was speculation a while back suggesting 5 car 158 operation of the Liverpool-Nottingham route. Not familiar with the northern end of the route but do platform lengths preclude 6 car operation? This would obviously require the creation of around 8 x 3 car 158s from 12 x 2 car.