According to the (quite reputable) seller, they're "ThroBak ER-MVX humbuckers" .
According to the spec sheet Collings sent me when I asked for it, they're "Throbak ER Custom Humbuckers".
As to what Throbaks I'd choose if I was choosing, I'm not the right person to ask, I don't know much about the details of what they offer. I hadn't heard of them, and maybe Collings either, don't remember, until I played this guitar in my most local shop, dug it a lot, and asked here about both.
@Andy Eagle spoke very highly of both, as you've probably seen, and I think some other folks too. I went back to the shop multiple times to play it, eventually got over my shyness about the money, at least enough to pull the trigger, and the rest is history.
If I had to bet, I'd guess they'd work with you to figure out some likely candidates for your wishes, and might let you return ones that didn't float your boat. However, I MADE THAT UP!!! Talk to them!