The group's leaders -- Irfan Naseer, Irfan Khalid and Ashik Ali -- were found guilty in February of 12 counts of preparing for acts of terrorism, the BBC reported.
Prosecutors said the group planned to set off up to eight bombs, using timers to detonate them.
Naseer, 31, was sentenced to life in prison, with a minimum of 18 years, Khalid, 28, was given 18 years and Ali 15 years.
Eight other members of the group were also sentenced.
Rahin Ahmed was sentenced to 12 years, Ashik Ali's older brother, Bahader, was given six years. Mohammed Rizwan and Mujahid Hussain were each given four years. Four who traveled to Pakistan for terror training but later backed out of the plot -- Ishaaq Hussain, Shahid Khan, Naweed Ali and Khobaib Hussain -- were each sentenced to 40 months in prison.
Justice Henriques told Naseer, "Your plot had the blessing of al-Qaida and you intended to further the aims of al-Qaida."