Whatever the reason for splitting the Alderley Edge to Wigan/Southport service at Piccadilly, it would have been an opportunity to run the Alderley Edge section with EMUs. Trouble is, Northern is just as short of EMUs at the moment as DMUs.
There has been an EMU on Picc-Alderley Edge today (323232). That particular duty is a Stockport CMD start, so it may have been an EMU covering Sat/Mon/Tues too, I don't know. The other duty on the current Picc-Alderley circuit is a Newton Heath start, so we can be pretty sure it won't be an EMU.
There appeared to be fourteen 323s in use this afternoon, which seems to be the current maximum.
In addition to the DMU under the wires on the morning extra from Alderley Edge, there has been limited DMU substitution elsewhere in recent days. I was surprised to find a 156 turning up on the 1628 Liverpool-Crewe yesterday, and there appears to be a 2-car diesel on Liverpool-Blackpool as we speak. (The duty commences with two Liverpool-Wigans, which I believe were also DMU-operated).
The current favourite for DMU substitution seems to be the one which starts 0616 Crewe - Liverpool, which is an Allerton duty. It was a 2-car DMU today, not sure if it was a 150/2 or a 156, it had gangways.