There are about 75 medical cannabis dispensaries. It's a shifting number because they tend to open up and close down on a pretty regular basis in Canada. They tend to be concentrated in major urban areas. They have been shown, through research and otherwise, to provide a safe source of cannabis to Canadian patients who might need it.
They've been the primary provider of medical cannabis research in Canada thus far, because unfortunately the Canadian government hasn't been very forthcoming in providing funding for research into the medical efficacy of cannabis. Despite the switch over to the new MMPR program, they continue to exist and provide medical cannabis to patients.