Have to agree with Tom on the above... The only "Northern" workings I'd consider 'rare' is if the service was meant to be allocated a Northern single decker, but a double decker appeared - and vice versa. Loans too, otherwise they're not rare at all...
Minus the 1, 2A/C, 60/61 - I'd say that the SPD workings you've given happen pretty much daily, if not every other day.
With Merits consumed on "Great Park" service X40 a lot recently due to 4950/1/2 being VOR a lot, it has been quite common for other Northerns to be used instead of the more common B10BLE, for example.
RE: Go North East - Latest