The information I'm looking at is updated in April 2015, so its after the new regulations
The 1.5% cap is the average rate including all card types (basic, world, and world elite)
For world elite, basically the minimum interchange will be around 2% (for large volume merchants, supermarkets, gas stations), and goes up to 2.5%

You can Google mastercard interchange canada 2015 to look at the PDF.

I do see your point though, as even with what I said, the average C1 world elite interchange probably comes out to only 2.1% to 2.2%. If they're paying out 2% in rewards, their margins will be very thin. That's probably why the updated C1 Travel card is so terrible, and also I expect that terribleness may get even worse.