I’m not sure if that is the intention. The unbranded E400MMCs have started turning up on the 41, 60/60A, 61 services. Not to mention the 57 and the 10. I think they were just to be used on services out of Caledonia which can be just about anything.
Seen one on the 38 at the fort yesterday. Seen them on the X85/X87 before too. Also seen the E400s from the 6s on the 41/60/60A a lot too recently