Lets just put it in another term, after sales service
Besides, the other mech wouldn't know what did the previous 1 did to your car, so if Mech B was the 2nd mech that the customer turn to after mech A's service, whatever latest things (alignment in this case) that has been done by Mech B should be clarified with Mech B only

AFAIK, there is no so called warranty for alignment, just after sales service, anything wrong bring back again. If still wrong and fed up, go to another 1, try to settle it and pay