The Byzantine Catholic church has always kept strict fast on Christmas Eve and continues to do so.
Little known fact: Poland, although Roman Catholic today, was originally introduced to Christianity through the Eastern church.
Many Polish customs for Easter and Christmas derive from that time or are influenced by their Slavic Eastern Christian neighbors. Another such interesting custom is the blessing of baskets on Holy Saturday. I have seen it promoted in Latin parishes in my area as a nice Polish custom, which it is, but they hold to that custom along with their Eastern Catholic and Orthodox Slavic neighbors who were all evangelized through the initial efforts of SS Cyril and Methodius.
Southern Italy (including Sicily) was once Byzantine as well. There is still a remnant church there, most of the inhabitants have been weaned away from the Byzantine rite over the centuries. Most southern Italians should be able to trace their ancestry back to Byzantines at some point. I would say that many of the customs there would have been influenced by the Greek church in some way, this could be an example of that.
+T+
Michael