You can make terrains in T.Ed which can be exported / imported into FPSC X10.
You can't manipulate the terrain geometry in FPSC but you can place entities and segments with it although you'll need some patience to do so effectively.
Ideally you want to place all of your entities with the terrain in T.Ed before exporting rather than adding them in FPSC.
See link below for a low poly terrain I imported into FPSC X10 from T.Ed. The enemy collision works well on flat surfaces but they walk through anything vertical unfortunately.
http://www.youtube.com/watch?v=ONIsr725RgM