If you use 'Send to Max' from AIM, your temporary fbx file and .pos (position file) are dropped in this location.
You may need to retrieve it if you need to export other data from AIM or Civil 3D again and coordinate the data in Max. You will have to use the .fbx export this time to add the user shift in the model as you may not get the same shift applied by the 'Send to Max' option if you select the region to export differently.
Make sure you copy of this data across to your folder where you save the Max file as if that content is deleted your textures disappear in Max as they are being referenced.
Images in 3ds Max Design not rendering correctly?
If using trees in your scene which have come from AIM, you may need to set some material settings
Press M for the materials and select the dropper and click on a tree to select the correct material
Set the specular level, glossiness and soften to 0
Select ‘M’ button next to opacity and point to the alpha channel of the tree image texture.
(Thanks to Bob Prokopp for pointing me in the right direction)