The normal way to do this is:
Map tiles can be mark of a type, there are 10 options:
UFO Power Source
UFO Navigation
UFO Construction
Alien Food
Alien Reproduction
Alien Entertainment
Alien Surgery
Examination Room
Alien Alloys
Alien Habitat
Most UFO walls tiles are marked as Alien Alloys and a UFO Power Source seems to have code attach to it to give 50 E115 also it seems to have code that meens it has a 75% to be distoryed when shot down instead of landed.
Also you could equpt Aliens to carry the gear you want to give to the player. for example the Alien on a very small is coded to always carry a mind probe inorder to give the player more loot and make the mission more worth while.