I don't believe the old analog Lear autopilot was ever able to receive RVSM certification so the aircraft would presumably have an updated avionics package, including a new autopilot, to legally fly above FL 290 in the U.S. or Mexico.
Oh, hell, didn't think about that, quite right you are.
Of course, in light what has been revealed here so far about Mexican bizjet operations, maybe the RVSM certification for this aircraft was 'undocumented'.
Thus my comment about a working CVR. This whole deal seems to be a bit shaky. Sad out come regardless.