Unfortunately almost a year later I am still working on the blackboard_six import format !
The first problem is : are you able (you or your server's administrator) to replace a file on your Moodle server installation by a new one ?
If the answer is no, you will have to wait that this problem is fixed in a future (not too far away I hope) version of Moodle and that your server is updated with this new version. Your only option until that is to use Gary Blackburn MoodleXMLBuilder to convert your testGen files into Moodle XML files that you will be able to import into Moodle 2.2/2.3.
If the answer is yes, then I can send you the current version of my work that (I think) is able to import nearly all TestGen files. But as I said you need to be able to replace some files on your Moodle server by the ones I can send you.
If something is unclear in my answer don't hesitate to ask further explanations.
In the meantime it woulf be very usefull if you can send me some of the files you want to import because the more examples files I can gather, the more I can improve my code to make it better. You can send the files to vedrine _at_ vedrine _dot_ org.