All Northern have been given so far are 14 trains which will allow some existing services to convert to electric traction on Phase 1 & 2. albeit with an increase in capacity on those services. Further phases of the North West electrification are scheduled to be completed by December 2016. The Transpennine electrification is scheduled for completion for December 2018 will take trains to York and the potential to convert more services to electric traction.
Northern currently operates a fleet of roughly 150 diesel train sets, and whilst some would still be required to service none electrified lines, that means roughly a shortage of about 50 plus units assuming all 86 319 sets were sent north without taking into consideration further schemes that could be added on to the so far announced scheme. There is no guarantee that all the 319 sets will be sent to north and if Northern (or whoever holds the new franchise) has to refurbish them, they will need additional units to cover the diagrams as we know them now. If the NW electrification puts more bums on seats, as it is hoped, even more train sets will be required, so a use could be found for any available and serviceable units for many years to come.