There's to be no new maintenance depot specifically for the new CAF stock, it'll be maintained by Arriva not CAF.
I think this will be a problem for Northern, thanks to geography and lack of a wired route over the Pennines.
There will have to be 2 electric sub-fleets, east and west, otherwise there will be lots of ECS working to/from depots, diesel hauled until the Standedge route is wired.
Presumably all the incoming transfers from other TOCs will go to existing depots - Newton Heath, Neville Hill and Allerton - so no problems there.
But the new CAF stuff really should have a dedicated depot like Siemens has at Ardwick, with some outstations for light servicing.
I'm sure Newton Heath won't be wired, and it would need a major upgrade anyway for the CAF kit.
Longsight is shared with Virgin and owned by Alstom (as is Edge Hill - it looks like Hitachi is using Edge Hill for west-side AT300 servicing (main base at Doncaster/Craigentinny).
Allerton is probably going to be full of 319s and logistically in the wrong place for CAF servicing.
But splitting the servicing between 3 or maybe even 4 sites (1xdiesel, 2xelectric) seems a bad idea.
Personally, I don't fancy Arriva maintaining completely new kit without a great deal of input from the manufacturer.
They do own the specialist ex-LNWR facility at Crewe (now Arriva Traincare), but in the past that has mainly been used for commissioning rather than fleet maintenance.
Meanwhile Ardwick, which looks like running down, would be ideal but is in the wrong ownership.