Is a specific type of bag needed (3-1-1?) to take liquids under 3 oz on a plane in YYZ or will putting all liquids in any sized plastic bag do?
Technically, yes, they want the baggie of freedom. They have a supply of them right before security, so you could transfer your liquids into one at the airport.
In practice, my liquids usually go through in a washing bag with one clear side that stays in my bag. This has never caused me any problems and I have not been asked to move my liquids into a baggie. (I don't count taking the bag out and looking at it, or putting my luggage through again without the washing bag, as problems. No one has ever rebuked me or confiscated anything.) When I am checking a bag, my carry-on may have hand lotion or hand sanitizer just randomly in a pocket and this also does not cause me trouble. However I am using the Nexus security line, and staff there may be less picky than in the general line.
They did not mention a specific named type, but they provided the exact sizes for the allowed 1-litre plastic bags along with the required features, from catsa.gc.ca (linked in the official Pearson website):
Containers of liquids, food and personal items in your carry-on must be 100 ml/100 grams (3.4 oz) or less. All containers must fit in one clear, resealable plastic bag no more than 1-litre in capacity. The bag must be transparent so screening officers can easily see the contents. - See more at: http://www.catsa.gc.ca/liquids-food-personal-items#sthash.fZwNbYKE.dpuf
Each passenger is allowed a single 1-litre bag containing liquids, food and personal items. The approximate dimensions of a 1-litre bag are 15.24 cm by 22.86 cm (6 in. by 9 in.) or 20 cm by 17.5 cm (8 in. by 7 in.).
So I guess you can not take any other size, because any other sizes other than the mentioned ones will not make a 1-litre bag. Although I think less that 1-Litre will be fine.
I used the bag that came with various size containers from the dollar store (a whopping CAD $2 plus HST) and there was no problem. Quality of both the bag and containers seemed okay.
I've been through YYZ many times with zippered 3-1-1 bags. The first was repurposed packaging that originally contained pillowcases. That was replaced with a zippered cube produced by Tom Bihn. Both were made (mostly) of see-through plastic and were approximately 1 litre in volume. Both were satisfactory. In fact, both have been acceptable at airports in many countries. As a backup, I carry an empty ziplock bag just in case a screening agent takes issue with my zippered bag.
I have travelled domestically and internationally with a purchased clear tsa approved zipper bag and always, always cleared security until this morning in Pearson. I told him and asked why and when did this start - he said always. So I had to transfer all my stuff from my clear “approved” bag to their zip bag. A huge inconvenience.