Preparation for laying ceramic tile
The thinset will not stick to the smooth finished floor.  You could just screw and thinset down 1/4" concrete board over it though and then install tile like normal.

Another option I would not recommend but is an option is you can probably lay tile over them with mastic instead of normal thinset.  But you will not be able to walk on the floor for upwards of 2-3 days minimum  AT ALL, longer with larger tiles.  You need that mastic to setup completely before grouting it or walking on it.

I don't think mastic is designed for a floor application though, but I do think it sticks better more like glue so it would stick better to the smooth finished floor.  But that "glue" is softer than thinset and cannot take the beating of a floor the same.