Remember, the key word here is INVOLUNTARY.

AA did some "involuntary" schedule changes on the flights I was booked on for my AONE3 ex-Canada (the North American segments were before my "first international over the water" segment, and the fare rules do not allow changes to those flights)and the new times were not convienent for me.

I called CX (who issued my ticket) who agreed to rebook me on flights that were "convinient" for me, and they told me to go to their airport ticket office at YVR. All they did was pull the affected flight coupons and replaced them with new flight coupons for the sectors in question (there was no need to re-issue the ticket). If I remember correctly, the new flight coupons had "INVOL" printed somewhere on them.

Anything that is INVOLUNTARY can allow fare rules/conditions to be overrided.

So, if you are on a flight (one segment) that was cancelled (INVOLUNTARILY, not by you), and you are required to take two flights (two segments) to reach your destination, the airline should pull the affected flight coupon and "exchange" it for "two flight coupons" (with INVOL printed on them).

Or in the worse case, they can issue you a FIM (i.e. the airline has already pulled your flight coupon and you are in the gate area, and the airline cannot find your original flight coupon) and even accomodate you on another carrier!