That utility is by Green Gandalf
Thing is only dynamic objects could be multi textured in the way described above, I am not even sure if Reloaded still does this.
Unfortunately only way around this is to either split the leaf canopy from the rest of the tree and make it two separate entity's or merge the textures into one and re-uvmap the tree. Maybe you can find a way to export them separately.
I do remember Lee mention something about his receiving one this way for testing, as collision on lower hanging canopy was causing issues, but if the tree is tall enough then you wont have this,not heard anything since. Using poly collision on trees must cost a lot performance wise so it's best to separate, still this makes it a pain to randomly place a lot of them, perhaps he still intends to find a compromise for this or a way to link entity parts for placement would work better. If the construction kit would import these parts to make prefabs of them then the problem is solved, but ideally the trunk should have poly collision and no collision for the canopy.
If they are dynamic they should be enabled for scripting to turn off collision and an invisible collision mesh used, again could be done in the construction kit, it's a pain all round when it comes to trees
Perhaps the ability to reduce the collision box scale to the width of the trunk would be an easy way around all this, I know it's a lot more than you asked for but it's all pertinent and something which needs looked at sooner or later.