This worked for me in JMP 10.0.0
Building off of DavidQR's example:
open("$SAMPLE_DATA/Big Class.jmp");
gg = Overlay Plot( X( :height ), Y( :weight ), Separate Axes( 1 ) );
axis_setting_Min=(report(gg)[axisbox(1)]<<getscript())["Min"];
axis_setting_Max=(report(gg)[axisbox(1)]<<getscript())["Max"];