User blog comment:ISharkyShark/What has been added since November?/@comment-32742453-20170914124917/@comment-30139169-20170915012206

@Echoplays Minecarts with Furnaces are not in MCPE. They were thought to be confirmed for Update 1.2, as its command string was in a GIF, but Helen later confirmed it was "leftover" string, and that Minecart furnaces were not coming in 1.2. If you don't believe me, go onto Classic UI and type "Furnace". Also, Minecarts with Furnaces are considered a "dead feature", and Mojang has talked about phasing them out (A.K.A. removing them).

https://twitter.com/jeb_/status/699241247391772672