I Opened Minecraft PC And I Checked The Update Log. On One Of The Lines It Says 'Added Command Block Minecart' So I Decided To Create A New World On Creative And See If It Is Actually There. On The Compass Icon For Search I Typed 'Command Block Minecart' And Nothing Appeared. Then I Typed In 'Minecart' And Still Nothing Appeared That Had A Minecart With A Command Block In It. So Can You Actually Add A Command Block Minecart?
Same reason as MC-918
Do /give @p minecraft:command_block_minecart