The men were found guilty of rape, unnatural sex and abduction. Three of them were also convicted of gang-raping another women, a photojournalist, within a month at the same mill compound in Lower Parel, an up-and-coming district where trendy bars and offices have sprouted on the sites of old factories.
In that case, the sentencing has been delayed till Monday.
"This court has to take a stern view of crimes against women so that a proper message is sent to society," Judge Shalini Phansalkar Joshi said, adding that the court had to "respond to the cry of the victim."
The men, sitting together at the back of the courtroom and surrounded by police, looked down and wept as their sentences were read out.
Mohammed Salim Ansari, Vijay Mohan Jadhav and Mohammed Kasim Hafeez Shaikh have been convicted in both cases. A fourth man, Mohammed Ashwaq Sheikh, was also jailed for life over the telephone operator case, while another convicted in the photographer attack, Siraj Rehmat Khan, will learn his fate on Monday.
The trials of the two gang-rape cases at Shakti Mills were completed in seven months by the fast-track court.
The 22-year-old photographer was on assignment at the mill with a male colleague when a gang of five men tied him up and took turns to assault her. The judge found her rapists guilty of offences that included showing pornography to her and forcing her to perform similar acts, stripping her, and destroying evidence.
The phone operator came forward after reading about the photographer's ordeal.
Police described the photographer's attackers as unemployed school drop-outs, while neighbours say they were a gang of youths known for petty theft and drinking in the area.