Drop Pod Question

I've heard reference to "Purifiers in Drop Pods" a few times around the internet now, but last I checked Drop Pods were only ever available to non-GK Imperial Power Armor armies as a Dedicated Transport. As I understand the Dedicated Transport rule, the only way to start the game in one is to either 1) be the squad it was bought for or 2) be an Independent Character attached to said squad. I have also heard the phrase "Drop Pods bought as Fast Attack" passed around, but I have no idea how this would be done.

So, to the meat of the question: Am I just missing a rules entry somewhere that would allow you to take Drop Pods in a slot rather than as a Dedicated Transport? If so, could someone point me in the direction of said entry?

Space Wolves have them as a FA choice.

Ah, so I was simply scouring the wrong book.

So two chapters who were in a cold war with each other are now cool to let one another borrow each other's rides. Got it.

Basically. Horray all imperial factions being battle brothers!