I can't say I've at any time analyzed CP's financials but I would imagine that oneworld could have at least helped CP by guaranteeing the operating leases which might have resulted in CP saving a few percent. I estimate this might have been worth around C$60m a year pre-tax if the indebtedness was C$3bn as stated.

Some sweetheart lease deals such as the one UA (or LH?) did for AC by subsidising leases on aircraft would have helped further, as would have even passing down some 737s (since BA is going to get rid of its fleet).

Who knows what the details are but I think deep suspicion will remain that somethign viable could have been done.