The number of different types of trees, as mentioned by Lewis above, is revealed by listing the dependents of the route in CM. The exact number of each type of tree will be a mystery for there is no way of counting them.
In the route asset Trainz must keep track of where every asset is located, their orientations, heights above (or below) the terrain, etc but this data will be buried deep within the .map and other proprietary data files.
It would be great to have a tool that will allow you to find that individual "pesky asset" you accidentally added somewhere.