I was at the tower some weeks ago. It's definitely possible for you to ride up there, there is a very smooth wooden path going all the way - but I don't think you will be allowed - too many elderly people etc. Maybe if you call ahead and arrange it in advance at a time where the park is closed, you have a chance. Esp. if you combine it with giving them some free marketing maybe.
Also I would hope no one would try something like this without permission? That's exactly what would give EUC a bad name. You already have people being scared at the upper level, clinging on to the guard rail for dear life - if you zip by on a vehicle they've never seen before, you are sure to scare them. Scared people are unhappy people.
In any case you can't, there is a checkpoint at the bottom with an employee checking tickets.