Being asked for a new medical examination means your old one has expired. It may mean they have decided you are not excessive demand.
I know I've said this before, but it bears repeating: the issue for people with HIV is the cost of medication, not the medical condition itself. If the cost of your drugs is below the threshold, then they won't issue a fairness letter. For the drugs you list, it is actually nuanced, because 3TC (Lamivudine) is inexpensive as it is off patent. Efavirenz ("Sustiva") has recently also gone off patent as a stand-alone drug. Tenofovir is still on patent in Canada, but it expires rather soon. Thus, it is distinctly possible that a medical officer did a cost estimate that did not conclude your cost was above the threshold (~$31,000 for 5 years).
That's consistent with being asked to do a new medical - if the old one is stale, they need to confirm that your medical situation remains the same.