Flew DFW-MEX-CCS r/t last week with a long layover in MEX.. (DFW-MEX was on AA metal). Lots of new oneworld signs around MEX. I was able to use the Biz checkin line with no problems. Also was able to use the MX Lounge (upstairs from the Admiral's Club) as a AA PLT. Returning from CCS, didn't notice the separate biz checkin line at first but by then was already through the main line. At checkin in CCS my boarding pass stated my oneworld PLT level. On boarding they mentioned PLT/GLD/oneworld members could board first.