Interesting. Probably some default setting on IVR systems that typically is not changed.
I find that 0 works often too. There are actually ways to hack a lot of these systems to get an outside line for free long distance. I've never would would never do it myself, but at work I get notifications from the security dept about customers being hacked and I have to go in the switch on our side to block long distance so they don't end up with a ridiculous bill. Basically a favor to the customer really... they get notified that their system needs to be patched. I think it's usually through the voice mail system that it happens. You can hit a certain key sequence and get an outside line basically. The calls typically don't last more than a few seconds and are always overseas. Kinda interesting really, makes you wonder if it's some kind of bot net doing this, perhaps for some anonymous transaction of sorts like sending faxes or even some kind of data packets. Could probably transfer bit coins that way actually.
My favorite is calling hydro companies. They always ask for the phone number associated with the account so they can tell you if power is out in your area. That's great and all but that feature NEVER works, it always says it can't find your account. For Ontario AND Quebec, both of their systems, I have never actually gotten that feature to work despite putting a valid number. So now I just spam a bunch of stuff until it gets me to an attendant. The Hydro Quebec one you have to actually talk and it has voice recognition so I always say "code postale inconu" and it brings me right to an attendant.