Changing YYZ terminals after security?
 

Will be connecting to a T3 international flight in YYZ after arriving in T1 on a domestic AC flight. FWIW, the reservations and airlines are totally different.

If I do not check bags, is it possible to switch terminals and connect directly to the T3 flight without exiting and re entering security?

No. The only way to change terminals is landside.

I'm not 100% in agreement. 99.99% yes, but there is one other VERY VERY remote possibility. The BMW service that no one really knows truly how people are selected. There is a slight chance that if you were selected for the service they could take you to T3, the only thing is that in the case of the OP, how would AC know in advance that you were connecting to a different airline. Normally (haven't heard of any examples otherwise) the car service is for domestic-international connections within T1.

OP - there is no publicly available landside connection or service that allows travellers to freely go between T1 to T3 or T3 to T1 traveling on any airline to any airline in their respective terminals. You have to go ground side using the terminal link train service.

The ground side terminal link service is 24/7 although during slow hours only one of the two trains are running.

I feel like the odds of winning the lottery are better than the odds of this happening :)

Winning the lottery, and having the BMW upgraded to a luxury mini-bus outfitted with a fully stocked bar and a massage table, and operated by the Swedish Bikini Team.

Come on Adam, aim high :-)

Not sure I would want to catch my next flight if that came to be! ;)

I agree but it's still not zero

Although nothing is public, the service selection includes full knowledge of the itinerary and would only pick up someone connecting to an international (AC) flight in T1. It is not a lottery where passengers are selected from a random draw and greeted with a limo asking them where they might want to be driven. Nice thought but I think we can firmly round that 99.99 to 100%.

And as long as they haven't made public the selection process (and then follow the process accurately without exception, and we all know how good AC is at following their own rules and training their staff to know/follow the rules) there is a chance..... very small, likely insignificant, but still a chance.

It's zero.

Prove it. Do we know the official publish rules/selection process?

Not publicly possible, but it's zero. Do you have a RAIC? Show me the tower sometime and I'll show you my workplace :D

I don't need a RAIC to show you the tower, or the centre, but I could do that anytime you like

Considering my AC ticket is in A class, I have no status on AC (or any *A carrier), and the terminal 3 airline is a OW airline, I would lean toward 100% as well ;)

I guess if I manage to befriend an AC VIP who is connecting through to T3 on the first flight, and s/he explains my situation to ground staff and asks them to let me tag along, then perhaps I could.

...aaand back to that winning the lottery comparison :-D