Maybe that article helps...
http://www.canaryadvisor.com/parakeet-mites.htmlI don't think the mites can be transferred other than by contact. So if you thoroughly wash your hands after handling the canary cage your parotlet should be fine. I would put them in different rooms though, just in case.
My budgies had scaly mites at one point (infected by a bird that I got in a pet store... never again!) and luckily my finches who are in the same aviary with the budgies were spared. I changed the branches and perches though, just to be safe and had the budgies in a separate cage during treatment.
I would bring the canaries to an avian vet though if you have one nearby and can afford it, just in case... I didn't treat mine myself, but let the vet do that with injections that he said was more efficient than topical treatment that you can do at home. It was rather expensive though, because I had to bring them in 3 times over the course of 2 weeks.