I don't know of a way to actually have all distros share the same menu.lst and update it accordingly, but one trick you can use is:
If you put that in the menu.lst of the Grub that gets loaded on start up, then it links to the menu.lst of the other "Linux Distro 1". Thus when Linux Distro 1 updates its menu.lst, you will see the change. The disadvantage of this method is you have to go through two boot menus to get to Linux Distro 1. Let me know if you need more info/details, but that's the general idea.
title Linux Distro 1