Then there must be a split because the Ukrainians here definitely celebrated on the 25th (I know a couple) per the CBC article.
In fact, if you Google for "Ukrainian Orthodox Church Christmas" most of the articles are about the switch.
BBC:
The move to the Western calendar is seen as a further shift away from Moscow's influence.
www.bbc.com
Time:
In the past, Ukrainians observed Christmas on Jan. 7, in accordance with the Russian Orthodox Church. Not this year.
time.com
France 24:
Many Ukrainians will on Monday celebrate Christmas Day on December 25 for the first time, after the government changed the date from the Orthodox Church observance of January 7 in a snub to Russia. Ukraine…
www.france24.com