(Sorry no pics or videos, I no longer have a WC account)
In Battle for Gilneas PVP, the actual Mine in the mine flag area is gated off.
However, this gate can be blinked through easily by mages. I haven't checked but it seems
likely any of the common wall-bypassing methods will work also. The mine seems to be
an exact copy of the mine in the gilneas starting area, and there doesn't seem to be any
way out of it. There are various videos on youtube of people accessing and exploring the mine.
When attacked by non-mages, a mage can blink in there and escape without the enemy
being able to follow. This can be useful, especially if you can send your elemental, demon
or pet outside to harass the enemy.
However, a really useful trick is to blink in there and take the enemy with you. This can be
accomplished in a number of ways.
The first and most obvious way is to taunt a subtlety rogue or a warrior repeatedly and lure them to
the mine entrance. Blink inside the mine and continue to taunt them. They will often charge
or shadowstep in there after you. They now have no obvious way to get out and are trapped there
for the remainder of the battle.
Once they are in there with you, sheep them and blink back outside. What usually happens then is that
they stare at you sadly at the mine entrance, or go and explore the mine. Either way, they
are completely out of the game, which will usually guarantee a win for your team unless you
were hopelessly outmatched to start with.
(If you are ever a victim of this exploit, just use "unstuck", you'll die and rez at the gy).
You can get other classes trapped in the mine if you have the engineering MC trinket on your belt. As
before, blink in there. Whoever is chasing you will usually stare at you dumbly. Mind-control them
and bring them inside the mine (make sure you are familiar with the pet controls). For some reason
pets (which your MC victim temporarily becomes) are able to walk through the gate. Now they are
stuck in there with you.
This glitch would potentially be even more useful to other classes (you could imagine a DK could pull an entire
team in there). I never had high-level alts so you'll have to experiment with that.