No, the maps are loaded by each console from their selves. If you have a modded map with it's own name (like mymap.map) and have it added to the mainmenu.map, noone will be able to play it unless they have that same mymap.map on their xbox. You can, however, name your modded map as one of the current ones like ascension.map or lockout.map and have SOME of the mods loaded on the joiners xbox. Weapon mods [not visual effects], physics, and a few others. Things like new skins won't be shown, nor will sounds. And by visual effects I mean if you change the contrail or the explosion, it won't be seen by the other person.
Now mods like flying warthogs. They can see it, then can ride in it in the turret and the passenger seat. however, if they sit in the drivers seat, they can only drive it because their game doesn't know to give it banshee physics.