The bearing that Surly spec on their track hub is an "angular contact bearing". I know this, because when I had a rear Surly hub, it too (well, the drive side bearings), destroyed itself. When I brought it into a bearing shop, after my LBS, using the serial number on the surviving cartridge bearing, was unable to order another set. I did not buy the wheel at that bike shop, I bought it from a dude at another bike shop.
With the serial number of the bearing, I went to a bearing shop here in Toronto. The dude at the counter told me that the serial number was for angular contact bearings. He explained to me what angular contact bearings were. In a nutshell, they are designed to accept loads vertically/radially and laterally/axially, where many cartridge bearings are only really designed to accept loads vertically/radially.
It is in that sense that Surly has adjustable cartridge bearings. If you've ever taken a hub apart, you should understand.
I no longer use that wheel anymore: I got sick and tired of replacing the bearings every 7-ish months. I built another wheel with a Dura Ace hub (loose ball, cup and cone) and I repack/overhaul it every 3-4 months, depending on weather conditions.