Hi, Ignatius. I am a former Orthodox Christian who is now attending a Byzantine Catholic church. Before attending Liturgy, I contacted the priest and asked him what would be required for us to be allowed to receive communion at the Byzantine Church. He said, simply, that we should attend, pray, confess, profess the Faith (which is done during the Liturgy, the entire congregation professes the Faith), and then we could receive communion.
I don’t know if it was different for us because my husband, myself, and our two oldest had been baptized in the Roman Catholic church–we converted to Orthodoxy a year ago, and are now returning–but I was surprised and heartened at the warm welcome we received.
The way I understand it, the Catholic Church will give communion to Orthodox Christians. However, changing formally is a different issue. We have not changed over formally yet because we haven’t been able to get our youngest’s baptismal certificate from our old (Orthodox) parish. I do not know what is required in that case.