I took my GT Karoakoram down to NZ in a cardboard bike box and it was fine. When I returned, I packed it up in a similar box that my LBS down there gave me. I don't think anyone would rent a case for 6 months, would they?

Also, if you are in Auckland you probably won't want to be fixed as it is hillier than San Fransisco. And if you think Toronto drivers suck, I have some bad news for you.....