I run rather often through the tunnel which connects Moonglade, Felwood and Winterspring.
Its just a bit of pain to run through it without my epic mount :-\
But there is a simple solution to this problem which only gets you dismounted when you are through the tunnel
Its one of those "generate some lag" but i will tell you a bit more advanced method to generate the needed lag
Okay, i use a program named "DU Super Controler" to make the needed lag, you can download it there:
http://www.homeqos.com/DUSuperControler-Install.exe
Please notice, that you need windows xp/2000 to use it.
When you have installed the program and it is running you see, that you can limit the data transfer rates of all your programs.
Now you stay in front of the tunnel, change the download limit of WoW to 1b (which means 1 byte per second, you can also just input a 0, which would mean no data transfer).
Then you run through the tunnel, don't get dismounted, come to the end, put in U (for unlimited) you get dismounted then, and are at the end of the tunnel smile.gif
The program is commonly used for managing traffic and can not be disallowed by blizzard i think.
On the outside its just "lag".
How does it work ?
Its pretty simple, the server tells you, when you enter or leave a zone in which you cannot mount.
As long as your clients gets not told about that by the server you will stay mounted infinitely