Final update -- the ORD-AKL (NZ27) ended up taking off (albeit after a 45 min taxiing delay) notwithstanding that over 1000 flights were cancelled. Since that flight was not interrupted, there was no additional accommodation that NZ could/would do.

NZ was really friendly over the phone and actually most of the agents (I think I called them 100 times while at the airport in my attempt to see if NZ27 would be cancelled ) were genuinely empathetic. I know (as most of us on this forum know) that my staging flight isn't their issue/concern. My experience at YYZ was quite exciting. For those that care:

• I initially booked a 3:11pm direct flight YYZ-ORD on AA using Avios. I received notification at 12noon that that AA flight had been cancelled.
• I called AA but they were not willing to accommodate me on another airline since the ticket was an Avios ticket (AA had cancelled all YYZ-ORD flights by then)
• at around 12:15pm I scrambled to book an Aeroplan direct flight on Air Canada's direct YYZ-ORD flight at 2:55pm.
• Arrived at the airport -- checked in -- and everything seemed to be on track. Until 1:30pm when the flight got delayed to 4:15pm. This delay meant that my flight had the same departure time as the next AC flight from YYZ-ORD. This usually means one of them will get cancelled. On Flightstats I could see that my inbound flight was delayed in LGA (another horrible airport) such that it seemed impossible that it would get to Toronto before 4:15pm whereas the other AC 4:15pm inbound flight was 15 min away from landing. I decided to see if I could go standby on the scheduled 4:15pm flight, thinking that one was way more likely to actually take off. As "luck" would have it, as the agent was looking into it, my flight (the one coming from LGA) got cancelled.
• With my flight being cancelled, plus other flights that were cancelled -- I was now the first person in line that eventually grew to be over 200 people. This was when I was lucky enough to have a sympathetic AC agent that attempted to get NZ to release their ticket and book me on the AC YYZ-SYD routing. After 30-45 min on the phone with NZ that whole plan collapsed. I was now left with nothing.
• I ended up calling the priority line at Air Canada and somehow got them to convert my Aeroplan (YYZ-ORD) ticket to a seat on a United flight that was initially scheduled to depart at noon but was now scheduled to leave at 7:15pm. That still would have worked to get me to my NZ flight -- since my baggage was checked right though. BUT I knew this would be my last hope.
• I later found out that the United flight right before mine left Toronto, made it to Chicago but was told to turn around and go back to Toronto. So, I knew that having a confirmed seat really meant nothing given the chaos at ORD.
• After I had my seat on the 7:15pm flight there were a large group of REALLY angry passengers that disembarked (having now been travelling in circles) and were now told to go back to the counter to rebook.
• I was tracking the inbound 7:15pm flight (which was coming from ORD as well), and everything seemed to be going well -- until it was 5 min away from Toronto. Then I got the cancellation notice - that flight was cancelled.
• At this point I knew I had no other options -- except to hope/pray that NZ27 suffered a disruption that would allow NZ to reroute me.
• 50 min before NZ27 was to depart, I had to call it -- at that point the flight was still showing as "on time" and I didn't want to get hit with a no show forfeited ticket. I called them and cancelled. The only 'good' news is that they did refund me my full fare (no change/cancellation fee).

After getting home from the airport at around 9pm, I spent most of the night cancelling all of my Australian travel bookings. Overall, I may be in the hole by a few hundred dollars of non-refundable cancellation fees but all of my hotels were cancellable.

I don't know what the lesson is of this whole experience is -- I don't think I would do anything differently. I never would have booked to be at ORD the night before or even at 6am that morning -- maybe if I had originally booked the staging flight on Air Canada I could have been accommodated faster once things started to get ugly in Chicago.

As a group of us at the airport were commiserating, my analogy of airport travel is that it's kind of like a casino -- if you're not winning immediately, you're likely not going to walk away a winner. When things go bad at the airport, they tend to go horribly bad.