This bus isn't a trolley bus, it is an electric bus.

Does it have trolley poles? If does, it is classified as a trolley bus here. However, the difference between a trolley bus equipped with batteries and an electric bus is slightly unclear. An electric bus with batteries being able to re-charge in motion is classified here as a trolley bus.

Ah, I see, but I don't see the trolley here.

But there is a photo of the same model trolley bus with raised trolley poles: http://transphoto.ru/photo/1004173/

This is a trolleybus, in this photo you can't see the trolley because it's walking with the auxiliary motor (inside the city wall there are problems for the wires). The main propulsion system is electric with the use of trolleys. All trolleybus in Italy have an auxiliary system and a motor is preferred to the batteries because it is more economical. In Rome, trolleybuses with the possibility of running without wires also existed in the 1940s.
Also this trolleybus has a diesel engine as an electric generator and not batteries.

Thanks for your help. :-)