The way I do it is once you get to the loading piont the screen is cleard and then replaced with different bgtiles and boinderies so realy it's the same map but just gets rebuilt in a different way to make it appear as if you have warped to another area.
No you can probably do it in the same way just have it load the map instead of placing bgtiles ,but that's just how I do it I'm sure there's more ways.
