I have been a user of Train Simulators since MSTS in 2001 and now the DTG TS-2015 Train Simulator, badly in need of improvements to its scenery, in particular distant mountains, so that they look like as shown in UE-4 !
Not being a user of any graphics creating software, what does it take to convert existing older graphics scenery and other objects to UE-4 graphics, or do they have to be recreated, using UE-4 ?
You have to save/export your assets to fbx/png/jpg/tga/obj -> after that you can import them into the UE4 
But you also have to make sure that they have a collision () and when you use static lightning you should add a 2nd uv channel for your lightmap (://)
Also make sure to take a look at this page: https://docs.unrealengine/latest/INT/Engine/Content/FBX/index.html
Hi , sorry, can’t see your name in your Profile, having sent you a PM !
Thanks for your prompt reply, another competent Austrian at work ! 
Here is me posting in the US TS forum, being its top senior member !
Take care and SERVUS !
Otto
I will reply to your PM when I’m back at home