this is a good question. It depends which category you are applying in. As a spouse in family class all medical things can be waived (of course they will do the tests anyway). So if you are being sponsored by a spouse/common law/conjugal partner, there should be no problem. As a refugee it too will be waived. For all other classes (eg skilled worker) the excessive demand clause does apply.
This is how the government calculates whether you will be an excessive demand as has been explained to me by an immigration lawyer who specializes in hiv cases:
The annual cost per average Canadian in the health care system is about $4000-5000 (i can't remember exactly). To be admissible your estimated costs for the next 7 years would have to fall under this.
So are you inadmissible because you have HIV? Technically the answer is no. But even if you were newly infected, and stayed healthy for the next 10 years, the costs of routine checks would basically guarantee you to go over the annual average of $5000. For example, a cd4 test here costs about $240, viral load test (i can't remember but more than the cd4). Canadian doctors usually check both of these tests 3-4 times a year, plus other blood tests, plus doctors fees, medication. Most Canadians are not aware of how expensive everything is, but everything has its price tag. Moreover, if you are not healthy (eg low cd4), your immigration doctor will calculate the chances of you being hospitalized for an opertunistic infection etc... Also, i have heard that if you already started HAART this would deffinately put you above the annual average.
This goes with every disease... there is no special rules or categories for HIV. If you have diabetes type I you are basically in the same situation. It doesn't matter which country you are applying from. If you were coming from France and you had diabetes you would be inadmissible.
I hope this helps.