I have finished the set for Truck Drivers. I initially started with xgen within Maya 2016, however the production pipeline ran into several issues with referencing scenes into other scenes within Maya, with archives and collections not coming across or not working properly resulting in huge performance impacts on rendering, instancing issues and overall mess with the production.
As such, I moved to using a mel script that generates a particle system on a designated surface and then creates an instance at each particle location, this wasn't very efficient for multiple instancing meshes and resulted in a very geometric pattern on the landscape, however was very efficient when rendering and working. However, once again, the production pipeline hit a roadblock and the instanced meshes were failing when referencing into other scenes and were causing significant problems in rendering.
Finally, I have settled with the creation of duplicates of the original meshes using a python script that duplicates a set amount of objects for applications such as generating multiple duplicates of an initial mesh when creating blendshapes and combining it with a different python script that randomly placed the duplicated meshes onto the designated mesh, this produced a much more believable and random distribution of the foliage. In addition, the production pipeline encountered no issues when it came to referencing between scenes.
Overall the set looks very nice and suits the Director and production well.
Gallery of the set progression: http://imgur.com/a/9PUPO
A final frame example of the set using Mental Ray Renderer: