As reported in their recent Q3 earnings conference call, looks like SWN is actively doing at least minimal lease acquisition in this play.
I've found that the following parcels were all leased by SEPCO in the October 23, 2012 Bureau of Land Management auction according to data on the BLM website. SWN's new leases include lands in both Sheridan and now also Daniels Counties. Don't know if they are using anyone else to do leasing as well; maybe they've got more action going on there than they are letting on about.
T. 33N, R. 51E, Sec. 2, Lot 2 - Daniels County (41.64 acres)
T. 33N, R. 52E, Sec. 7, Lots 7-10 - Sheridan County (133.35 acres)
T. 34N, R. 52E, Sec. 9 N2NE, SWNE,W2SE10, Sec. 10 NENW - Sheridan County (240 acres)