Not sure what specific price you are referencing, but yes the Lone4 and 5 are good bargains in hard currency terms out of MPM, notwithstanding the recent fare increases. Naturally visa and positioning flites may increase costs, but that depends on each individuals situation.
Yes, it is possible to upgrade using AA or BA certificates on the respective carriers marketed and operated flights. Naturally all the rules of each respective instrument will apply, as on any other fare.
Note that, depending on the program used, mileage earning for either rewards or status may be limited. Nonetheless the fares remain attractive and offer quite low cpm (depending on routings obviously)