
It´s importing perfect manually, assigning uv´s with the right absurd Max tile values.
Can you take a look at some Cityscape fbx files (be happy to send you)!, since they import perfect to Octane via your script.
If GT can work effortless with Octane it will be a winner, the power of Octane with landscapes is amazeing, seems to not care of stuff that bring Vue/Max/Maxwell to a muddy slowmo.
All of them are useing instancing, perhaps the speed will drop with many reflective/transparent/AA proxy´s, I´m not the genious though (thank God).
I´m very happy with the state of both Octane/GT, if you don´t push the limits it´s rock solid.