Ioan Boboc, 22, suffered burns over 60% of his body whilst he and other workers were using breakers and a shovel during excavation at the corner of Charing Cross Road and Tottenham Court Road on December 2 2008.
Southwark Crown Court heard that Birse Metro had not informed workers that there were live cables in the area.
Boboc died of his injuries on Christmas Day 2008.
Birse Metro of Redhill, Surrey, pleaded guilty to safety breacjes and was fined £167,000 and ordered to pay £43,000 in costs.
After the hearing, HSE inspector Lisa Chappell, said: “The dangers associated with live underground cables are well-known to those carrying out groundworks in the construction industry.
“This incident highlights the absolute necessity for such work to be properly planned and managed.
“Operatives should be briefed on the presence of cables and a safe system of working should be robustly enforced.
“Mr Boboc’s family continues to grieve the loss of a son and brother following an incident that could have easily been prevented.”