This is a photograph of Cardinal Luigi Traglia saying Mass in St Peter's Square the evening Pope John XXIII died. [June 3rd 1963]. He finished the Mass moments before Blessed John XXIII died. I don't know why he is celebrating Mass in the direction he is as the East is in the other direction - that is why the High Altar in St Peter's is placed the way it is: facing East above the tomb of the Apostle.
As to the direction of the altar: I have seen many photos of the portable altar set up between the papal altar and that of the throne, and it is set up facing the altar of the throne [west]. The same can be said of photographs of Masses offered during Vatican II on a portable altar between the papal altar and the entrance into St. Peter's. Those Masses also being offered toward the west. So, it would seem that Masses at the Pope's altar, obviously, are facing east, but other portable altars set up face in the other direction.-Donnacha