I'm not sure I'd call zone system equitable. Does it makes sense that someone can travel from Pointe-aux-trembles to McGill for cheaper than someone who just takes the Metro under the river from Cartier to Henri-Bourassa? No not really...Good for Montreal on it's new fare integration.
The "zone" system is by far the best of all options. It is equitable, makes sense to the general public, and doesn't require a math degree to figure out your fare.
For a Zone system to be "equitable", I feel you need to at least have a base 2 zone fare system, so you don't have to deal with paying extra just for being at a zonal border.