The "how" is a matter of some debate. There are a few who say it's just a speed run, but a fairly adamant group is insisting there is some hack or exploit at work. I think I've done Resistance, but not this one. Honestly, I haven't done much outside the "main" storylines. I did Whiteout twice, the Viper one twice, and the alternate universe one with the giant Destroids once. My highest is only level 23, and, for various reasons, I have three different accounts.
On a side note, I got thinking, last night: I have three accounts, and my son has one. I now have four machines that have the game client installed. One more of each, and I can "double box" a full team and form a super group of all me!
Mwah-hahahahahahaha- <coughsputter>
Sorry. Anyway, yeah, I think it's just speed runners, too, but I haven't played it, yet.