I bought my car there and have the paperwork. It specifically says that they will replace the tires with the exact make and model or equivalent. The wear has to be down to the indicator bars on the tires. And if you check this CBC Marketplace
you will see that Mazda dealers were recently caught gouging for service. Mazda Canada denies any knowledge.

So tires for life....but at what cost?? (nothing's free! the dealer ain't giving them away) Count me a skeptic...