It's really easy, all it takes is correct timing. Which you can do yourself or with a friend. Here's how it is set up.
Find a nice cozy tower to exit the game from. Wait the 20 seconds. (Remember which AV you were in)
Once the game becomes available again, log back into your toon before the AV round starts. You'll zone into the spot where you exited the game from.
Ex.
I was gaurding TP but then had to exit due to coach aggro. AV 24.
Later on, I log in and QuaZam! AV 24 starts in 2 minutes! Free reign on towers
They fixed it so that it no longer shows who caps towers in AV a while back so no one will know that you did it. I'm sure that GMs keep a log though. Plus the scoreboard shows who capped what how many times or defeneded and such.
There is one bug with this glitch...
It doesn't load AV - which is why this works - so you cannot leave lol. You'll have to exit the game again.
Good luck and happy hunting!