(28 Apr 2016, 12:59 pm)anvil1984 wrote Incorrect again ALL York drivers sign 156s and most Leeds drivers. This is incase they have to take one at short notice from Newcastle - York / Leeds for a visiti to the wheel lathe at Neville Hil as Heaton does not have those facilities. 
It is not an occasional ECS it is a nearly nightly ECS move (northbound Knaresbrough to Heaton empties, southbound Monday to Friday its 2221 Newcastle to Darlington then empties to York) plus any movements as required. Usually 2 X 142 but can have any combination of 142 / 156.
142s / 156s do have set depot allocations however the unit diagrams can have a Heaton unit in Lancashire or it may have been as a result of a set swap at the start of the day. As mentioned if a Ex FNW 142 ends up in the northeast (especially the ex merseyrail examples) they don't last long before being swapped back

Heaton does have a Wheel Lathe as Neville Hill 158s and Newton Heath 142s and 150s have visited in the past for that very reason.
Though it isn't daily, If Neville Hill is busy on other units that's when they get sent up here.

Yes there is a Knaresbourgh to Heaton ECS after a peak time Leeds - Knaresbourgh, It is also indeed booked for 2x 142s though no 156 should ever appear there, 1x 142/1x 150 can sometimes happen at the most, The 1x 142 being a Heaton unit worked up the night before to work the day on Heaton's Diagrams in Yorkshire and the 1x 150 visiting Heaton for maintenance when Neville Hill is too busy.
If its 2x 142s then both will have ran up the night before and done what ive mentioned above.

Heaton Units are Diagrammed to appear in Lancashire daily, The Cumbrian Coast has a handful of diagrams utilising a Heaton 156 and on 1 or 2 a 153 attached too.
These units work from Heaton on either the Tyne Valley extension to Whitehaven or through a Tyne Valley service which terminates at the through WCML platforms around 1600-1900 time and works the next Cumbrian Coast service out.

Some North West units have ended up here though it Heaton 156s in the North West happens way more likely than a North West unit up here.