Aha, I think I just found the solution to the problem of the WW failing to launch when you select the BSG mod!
I was running version 1.0, as installed from the retail CD. I spotted a patched version with various enhancements and bugfixes on shapnelgames' website, which upgrades the game to version 1.1. After installing this, WW launches & supports the mod just fine.
The patch can be downloaded from
http://www.shrapnelgames.com/digital...d_worlds/6.htm