Airbus towing: is it necessary to switch on the Y HYD pump?
Please read fully the answer to understand the matter. 

Please be careful, with respect to the 320 it depends on the aircraft generation, as I remember if not all, some A320 landing gears are green operated. Nevertheless, by switching on the yellow electrical pump, the green circuit will be pressurized via the PTU, thus preventing the towing force to cause inadvertent retraction of the nose gear. 

This is just an explanation, not a procedure to be followed.