I have no idea what format you need for trees in EB, or how to implement them.
afaik in .cas files and in .item files (you need 3dsmax and vercis script to open those files)


Agian, ask caius or the napoleonic team.
Teleklos knows alot about this stuff, too ;)

The one who did this for the Napoleonic team, Duke John has recently quit RTW modding. In the Scriptorium you can find his Tutorial about modding vegetation in RTW.