Ian,
Very easy to make one of them drivable. The first thing you have to do is find an existing tram that you like and that has the driving charactistics and sounds that you like. View its config.txt file and write down the kuid numbers of its enginespec, enginesound and hornsound. Then clone one of the Bush Garden Trams and open it for Edit in Explorer. Double click the config.txt file and make the following changes:
1. Change the tag engine 0 to engine 1.
2. Change the enginespec kuid number to the number you wrote down above.
3. Add 2 new tag lines with their kuid numbers:
enginesound
hornsound
4. Change the username to a new name.
5. Save the config.txt file and commit the asset.
Take it for a test drive.
Bob