Pope Francis (then Archbishop Jorge) concelebrating at the Ukrainian Catholic Cathedral in Argentina.Perhaps this is the wrong place to ask this but I remember reading once that in the Catholic church when bishops concelebrate in another rite, they are to wear the vestments of there own rite, is this not the case? As it looks as if HH Pope Francis is vested in byzantine vestments(except for his trademark mitre).
Normally this is the case, but Latin bishops who have jurisdiction of an Eastern Catholic parish are allowed to vest and serve in the rite of said parish. In this case, as Archbishop of Buenos Aires, Archbishop Jorge was ordinary for the Russian Catholic parish and monastery there. That said he should have worn the phelon rather than the mantiya if serving or worn the mantiya without cassock if just attending in choir.