They ran into backhaul issues for each site in Chicago and didn't have the billing system ready yet. Baltimore might be first now because it's a smaller area, so easier to get fewer sites the backhaul they need.
I'd say that the billing issues were the real problem, which AFAIK they didn't mention prior to this latest round of developments. The backhaul issue seems to be "solved" with exactly what some watchers suggested, wireless PtP backhaul & dark fiber, which certainly (?) doesn't belong to Sprint. I hope they're able to make steady progress on this now without any major hiccups so that we can put WiMax thru its paces.
