Canaport LNG LP, Irving Canaport GP Company Ltd. and Repsol Canada Ltd., each face two charges under the federal Migratory Birds Convention Act that prevent anyone from depositing a substance harmful to migratory birds.
They are also charged with unlawfully killing Canada warblers under the federal Species at Risk Act.
Environment Canada launched an investigation after about 7,500 migrating birds were killed in September 2013 while excess gas was being burned off at the facility.
The defence has been granted time to review documents provided by the Crown on Thursday.
The companies are now scheduled to enter pleas on July 30.