Pesachim 85: The 'Lepers' at the Gateways of Jerusalem

A new factor in the permissibility of th Korban Pesach: What happens if the meat is taken out of the boundaries where it's supposed to be? Is that rendered impure by rabbinic decree? Plus, what does moving it out entail? How much is parallel to the laws of carrying on Shabbat? Also, what happens if a limb leaves the boundary... where you then can't break the bone? As compared to other korbanot, where you could break the bones. And in having the boundary - outside the door jamb, possibly. Plus, a description of the courtyard vs. gates of Jerusalem, which hones which boundary. But wouldn't the gateways of Jerusalem be pure themselves?! Those with tzaraat would make their way to the Temple courtyard via Nikanor's Gate, to become pure.