Our recent Canadian oddyssey was interesting airline-wise. We flew Air Transat (or Transhat as many who fly them call them). Emily, being an infact got NOTHING in the way of travel allowance, and Sue and I got a meagre 20 kg baggage / 5 kg carry on. To be fair, Emily was allowed a nappy bag free of charge as well as taking her push chair on.
We've just checked Air Canada for our return to Canada in May. Emily will cost 10% of an adult fair, which works out to be about £58 (not sure if it's 10% after taxes, surcharges, etc.) For this infant fee, she gets TWO bags at 23 kg each, as well as 10 kg carry on. Now I don't know if she gets a nappy bag for free, but this will be over looked given it's an allowance comparison of 56 kg vs NOTHING. Sure Air Canada are a bit more expensive, but when you weigh up the hassle that Air Transat seems to be, it's a no brainer.
Sue and I also get 56 kg each (Carry on might be a tad more). This works out to be well over 150 kg for the three of us, as opposed to what Transat offered us over X-Mas - 50 kg total for the three of us.