Ontario Ministry of the Environment: Environmental Assessment
Ontario's Environmental Registry does not list all environment projects, such as those involving provincial infrastructure (including roads, power structures and landfill sites). These are handled by the Environmental Assessment (EA) process which has its own set of standards and guidelines.
No common registry or search engine is available or planned - Environmental Assessment has its own search engine. I was able to find a wealth of information about the Durham waste-to-energy proposal that generated considerable local interest, since one of the proposed sites was nearby.
Note: this is a public post.