"averaging 40gbps" != "maximum 40gbps"

Also, qix puts their member list online, and Amazon has a 10gbps port: http://www.qix.ca/en/members/membership

From 2013: "deployed over 180 Gbps of capacity into the exchange." https://www.cologix.com/pdf/QIX-Case-Study.pdf

If we believe the Cacti graphs, over the past several weeks the Montréal QIX peaked at 50Gbps[1]. Your comment implies that the QIX might be running over a mere 40Gbps link, but presumably their aggregate link capacity is (much?) higher than that.

[1] http://www.qix.ca/en/qix/network

That's 40gbps of voluntary (technically settlement free, but not in the usual meaning of the term) peering, not paid transit. Paid transit numbers are several orders of magnitude higher, and total traffic numbers are unknown.

Amazon connections between regions are owned by Amazon. Only last mile traffic would need to go to an Exchange.