In my experience, the Canadian credit file will show the maximum balance that Amex ever reported on your charge card. And then it will report the balance on the day of reporting.
There is a guy on redflagdeals that works in the industry and answers questions in an epic thread.
The max amount shown is not a credit limit. (But, it is my understanding, a problem with the way the credit file data is printed out.)
In fact, the credit limit is zero. The utilization would not be calculated on the individual product (charge card), but overall utilization (all products) vs your overall credit (all products). That makes a lot more sense, too.
If all you have is your Amex charge card, your utilization would be infinite. But most card holders would have some credit product on their file.