Tried using terrain tools in Severnaya, works without crashes for me. Didn't try to move the TerrainInfo though.

Interesting that U2XMP code is extremely similar to UT2004, not like U2 code. Like, see the different Teleporters:
Unreal II: http://unreal.student.utwente.nl/uncodex-u2xmp/Source_engine/teleporter.html (the URL, stating XMP, is wrong)
Unreal II XMP: http://unreal.student.utwente.nl/uncodex-u2/Source_engine/teleporter.html (the URL, stating U2, is wrong)
UT2004: http://unreal.student.utwente.nl/uncodex-ut2004/Source_engine/teleporter.html.gz

Of course, the Teleporter is a generic UE feature, yet U2XMP code is essentially the same as UT2004, and even better, as it has teleport sound support!

No, custom sound. You only hear the usual teleport sound in UT2004, while the U2XMP teleporter lets you choose the sound to use.