For this exploit you will need the help of a friend.
This may work for heroics and Gear requirements aswel, tho I have not tested it for that - (think ICC 5 heroics)
My 79 friend wanted ICC normals, so I figured out a way to use the LFD tool for a fast group, and get him in, even tho he is not 80.
Step 1. Join the LFG, with a random friend (he will leave the group later)
Step 2. Enter dungeon as normal.
Step 3. Random friend leaves.
Step 4. Invite low level friend
Step 5. He clicks the eye for teleport to dungeon.
There you have it, a fast way to get into the ICC normal runs, and other instances, even if you are too low for them, or dont have the correct gear.
It probly wont work if you are too low to go through the portal to the instance, was unable to test.
I hope somone will get some use out of it.
Enjoy!