A MD80 FLT CREW EXPERIENCES A TCASII RA ON TKOF.

Narrative

TAKING OFF FROM RWY 31 ON BILKA 1 DEP. CONDITIONS WERE VFR; CEILING AND VISIBILITY BASICALLY UNLIMITED. FO'S LEG. OBSERVED 1 ACFT DEPART TO THE S OFF RWY 13; PRIOR TO OUR PUSHOUT; BUT WE WERE GIVEN RWY 31. CLRED FOR TKOF ON RWY 31 BY BJX TWR; WITH NO RPTS OF ANY OTHER ACFT IN THE PATTERN OR AREA. TOLD TO CONTACT LEON APCH WHEN AIRBORNE. NORMAL TKOF UP TO 1000 FT AGL. AT 1000 FT AGL/7000 FT MSL -- JUST AFTER CALLING FOR 'HALF RATE -- FLAPS UP -- CLB PWR' AS THE CAPT SWITCHED TO APCH CTL; WE GOT A TCASII RA TO 'DSND NOW -- DSND' WITH VSI RED AND GREEN ARCS AND A YELLOW RA SYMBOL ON THE TCASII/RADAR SCREEN AT APPROX 11 O'CLOCK POS AND SLIGHTLY HIGH. FO STARTED TO DSND; AS CAPT PICKED UP THE TFC VISUALLY. WE CLRED THE TFC WITHOUT ANY PROBS. THE TFC WAS A DC9; AS I RECALL; THAT APPEARED TO BE DOING A DOWNWIND ENTRY TO RWY 31. ONCE AGAIN; WE RECEIVED NO WARNING OR ADVISORY FROM TWR OF ANY OTHER TFC IN THE AREA PRIOR TO TKOF. COMMERCIAL FLT MANUAL; PART II; DOMESTIC COVERAGE PAGE FOR LEON; MEXICO; CAUTIONS THAT 'AIRSPACE IS UNCTLED BELOW FL200 EXCEPT AT AND BELOW 11000 FT MSL WITHIN 10 NM OF BJX VOR. BE HEADS-UP FOR ACFT NOT IN CONTACT WITH ATC.' MY EXPERIENCE AT BJX/LEON SEEMS TO INDICATE THAT IT MAY BE UNCTLED; EVEN IN THE ATA/CLASS D AIRSPACE.