Found this about them, makes sense considering the time.
Siege tram
During World War II, the work of St. Petersburg tramway changed completely. Operated and maintained mostly by women and children, they no longer just carried passengers, but were also used to evacuate equipment and valuables, transport fuel and convey the wounded. Due to power interruptions and snow drifts, by January 1942 the tram traffic stopped completely. Weakened by hunger and cold, people were forced to cover long distances on foot while empty trolley cars were disappearing into snow drifts, so restarting the tram traffic became a matter of life and death. After more than 150 km of overhead line had been restored, cargo trams resumed their service on March 8, 1942 and by April 15th five passenger tram routes were reopened. After that time, St. Petersburg’s tramway system never stopped working and by January 1945 the number of routes reached 20.
Cargo tram with wagon-dosage at Leonova depot (№2) in Saint