Now, that's one for the model makers to get their teeth into. I'm guessing that the tanks were brought to the railhead on the rollered dollies, seen on the left, towed by the traction engine far left.
Interesting picture! On page 24 of David Fletcher's Osprey book on the mark IV there's a picture of a female tank similar to the one on the right, being pulled along by a traction engine. It's hard to tell for sure, but it looks to me that it may have the cluster of three track extenders at the rear right in the same position that the one above does. Could it be the same tank?
Fletcher's picture is captioned as being at Cambrai and "is believed to be 158, which caught fire in Bourlon village on 24 November 1917". However is there a number on the armour plate on the fuel tank? Looks to me like *42.
One other thing, is one of the Germans wearing a helmet?