As others have said, Canadian McDonald's now has the old Tim Hortons coffee, and the new Tim Hortons coffee tastes like they brewed it with water they collected from a puddle in the parking lot.
Presumably McDonald's has different suppliers in other countries though.
McDonald's has Tim Hortons' old supplier. They don't have the same blend, and probably not exactly the same procedure for brewing it. The McDonald's coffee is much better than Tim's ever was since at least ~2000 when I first tried it.