That information came from Zurich's Stadtpolizei in a newspaper article. Their representative stated that the 3km/h limit was from the Bund, and they weren't happy about it either (yeah right!). If it is done differently in another canton that doesn't necessarily mean that the limit doesn't come from the bund, it could simply mean that they are choosing (probably illegally) to ignore it. But look at it this way - it's better for you if you live there.

Mark