I've booked numerous tickets from YYZ-LGA with LAN. Every agent you speak with will give you different availability, regardless of what is showing on aa.com. In fact I once got a seat on a flight that was showing no availability on aa.com. Also, beware of the taxes - very often they will give you taxes in the range of $80-$100 when it should be around $55 and no arguing on your part will help. You just need to hang up and call again. Although, I once had an agent put the ticket on hold for me and then when I called back they didn't have those flights available so she checked other flights and told me the taxes were around $55 so I then gave her the other confirmation number and she booked it for me with the right taxes. Good luck.