Wirelessly posted (BlackBerry: BlackBerry8530/5.0.0.1030 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)

"Currently, Air Canada won't even sell you a LAX-YYZ-LGA ticket unless you bought separate tickets."

That's because it's illegal for AC to sell transportation between two points within the U.S. on a single ticket.

The QF JFK-LAX and LAX-JFK flights are permitted, as long as passengers are traveling to or from Australia. (I'm not sure if a QF passenger can have a stopover at LAX, or if only true connections are allowed.)

And I'm pretty sure that Canadian law prohibits U.S. carriers from transporting passengers between two Canadian points via the U.S. on a single ticket.