The tradition of the Christmas Tree was introduced on the Hungary in the first half of the 19th century. First documented use was in 1824. It didn't hold right at that moment, took about a hundred years to spread everywhere.
Protestant nobles brought the custom to the Court in Wien then they passed it on. It seems the spread in Austria-Hungary was helped a lot by the K.u.K. Army, during WWI the units erected trees to celebrate Christmas, and then soldiers took the tradition with them home.