Also the marshalling of an empty four-wheeler between two loaded bogie wagons is prohibited because it creates a difference in the heights of the wagons which can lead to parting and/or derailments.While this is not strictly applicable here,uniformity...

Also the marshalling of an empty four-wheeler between two loaded bogie wagons is prohibited because it creates a difference in the heights of the wagons which can lead to parting and/or derailments.While this is not strictly applicable here,uniformity of the height must still be maintained hence the filling of water.This also enables the water filled wagons to be used as guard wagons.

That's probably because the tanker take is empty!! so there's no probable need of a buffer BCNA/BCXC/BOXN wagon.

Hmmm intresting to note that there is no BOXN or BCNA wagon behind the loco. Noramlly the line up is loco - BOXN/BCNA wagon - tanker rake - BOXN/BCNA wagon-Caboose!