Never knew they interworked on a Morning - this would have been around 8.30 (ish) not far from Houghton, so it is possibly still the case.
Just after 7 tonight, there was a 20a pulling into Park Lane worked by a Fab 56. Ive seen those vehicles covering the Prince Bishops a few times including a time I was using it - so not that unusual.
RE: Go North East