I found the cause of this issue, the PROJ.4 library is missing from the Arma 3 Tools package:

http://feedback.arma3.com/view.php?id=18123

We've actually figured out how to get roads working, and are doing it by putting this script into "p:\scripts\editor.sqs":

~.1
diag_log "Before Loading Roads";
result = buldozer_LoadNewRoads "P:/path/to/road/shapefile/";
diag_log "After Loading Roads";

The roads then display in Buldozer.

Perhaps a more elegant way to run the command would help? The Buldozer log files imply that the p:\scripts\editor.sqs mechanism has been removed and that the script is ignored, even though it still works.

I found the cause of this issue, the PROJ.4 library is missing from the Arma 3 Tools package:

http://feedback.arma3.com/view.php?id=18123

By virtue of using GDAL's auto-detection, TB already supports .BT files (and Terragen .TER, etc). You can force it to use them by selecting "All Formats" in the open file dialog.

I've opened Terragen files this way, and they work perfectly because they don't have georeferencing information.

However, .TB files do contain georeferencing.

The only thing stopping .TB support as far as I can tell is this issue:

http://feedback.arma3.com/view.php?id=18081