There's two X7/X8 Geminis (7606 and another) on the X10/X11 right now. At least one of them has made its way there after being on its correct route this morning.
7411 on the 308.
7806 on the X10/X11.
7445 on the X14.
Sapphire X21/X22 E400 on the X20 (though I don't know if this is a normal run-off)
1581 is on the X21/X22 in addition to 1580 mentioned earlier.
Also there's what I think looked like an MPD on the 43 too.
RE: Arriva North East: Rare & Odd Workings - March 2016