Don't know about Northbound, RTT has the n/b Doncaster - Shields as cancelled (http://www.realtimetrains.co.uk/train/P94136/2017/10/24/advanced).
318265 moved south to Doncaster though under 5E20 (http://www.realtimetrains.co.uk/train/K97172/2017/10/24/advanced)
They had the Saltire livery amongst other work done at Doncaster over the last few years, certain units are being sent back for retrofitting of things that weren't done initially. Not 100% on what's being retrofitted, heard a few rumours regarding cycle spaces but someone else on the forum may be able to give a more definitive answer.
Scotrail units reguarly work the ECML under power tripping between Shields depot and Doncaster for overhaul.
Plug sockets?