All but two of the 15 were originally charged not only with conspiracy, but also with premeditated murder in connection with the slaying of rival gang members.
Quebec Superior Court Justice Andre Vincent sentenced four of the 14 on Thursday.
Three were given prison terms of 12 years and seven months. With time already served, they face between another nine and 35 months in detention.
The fourth person was sentenced to 11 years and four months but will have only one other day in prison because of time already served.
The 10 others who pleaded guilty Thursday will be sentenced in the coming months.
Out of 156 people originally arrested in Operation SharQc, only 12 have opted to stand trial on charges of murder and conspiracy to commit murder.
Jury selection for 10 of the 12 begins Monday. The final two have a trial date in January.
Since the police operation, 101 people have now pleaded guilty, while 31 others were released in 2011 after a judge ruled there were unreasonable delays in their case.
Three people have died since being charged, while eight others are still at large.