Well I know this for sure based off the screenshots: They have power armor and they have enough of it to the point where it's for sale. So if they found a military cache that the Brotherhood, Enclave, or any other powerful faction managed to not find before them...it had A LOT of armor in it. T-60 armor to be exact which I'm guessing is better than the T-51b armor and possibly any Enclave armor. If they were short on Power Armor or got it from looting, I guess it would just be sold as generic T-60. But it specifically says Atom Cat T-60 which means it probably has some sort of custom work done on it and I doubt they would just sell custom armor if they didn't have a lot of it.
I have no clue how they got their armor though. If it was by looting, that's dumb and means they must have killed a ton of people wearing T-60. If it was from a military base/cache, that's also dumb as it means that a small group of damn greasers managed to find a large amount of high tech military equipment before a group like the Brotherhood could. Half of this is speculation though based off of the few screenshots I've seen so I could be wrong about some things.