I find it a bit odd that they'd have the resources to make their own MEC troops, ghost armor, etc, though.
I wouldn't be surprised if the aliens were secretly providing them with equipment to help 'even the battlefield'. It sorta ties in with their motives (which I can never exactly remember/understand).
Aren't they against the aliens too? I mean they're still human right, and it sounded like they were attacking aliens to steal their tech?
From the sound of it, they're exploiting the invasion as an opportunity to push their own agenda. They aren't 'against' the aliens, as in they don't think stopping the invasion is their responsibility. They also aren't 'with' the aliens, as in the aliens aren't giving them resources to fight humans. They're like looters stealing during a riot; they don't support the rioter's perspective, they assume the problem will be dealt with by
someone, and they're hoping to get as much benefit for themselves as possible before the opportunity blows over. It probably never crosses their mind that humanity as a whole could be wiped out if they don't stop disrupting the one organization capable of saving the world.
Note that the EXALT guys were using laser weapons; that's clearly stolen tech from XCom, not alien-delivered kit. And human-enhancing modifications isn't the kind of tech generally available from non-human organizations. It sounds like they're stealing tech from XCom, not getting direct support from the aliens. Maybe they've got a Thin Man infiltration problem at the highest levels of the org, though...