When I was trying to use the repeating command block, it wouldn't respond to redstone input and wouldn't run command.

Command Used:

/blockdata ~ ~-1 ~ {SpawnCount:10,SpawnRange:7,RequiredPlayerRange:32,MaxNearbyEntities:16,Delay:1,MinSpawnDelay:5,MaxSpawnDelay:10,SpawnData:{id:"Skeleton"}}

Get Mob Spawner:

give @p mob_spawner

Get Command Block:

give @p command_block

(repeating_command_block if you want.)

Steps to reproduce:
1. Pace down the pig spawner(It turns into a pig spawner on placement, not a bug.)
2. Place a command block somewhere else and put in command at top.
Be sure to make sure the third button is Needs Redstone, else the command will fire 1 or 20 times a second(prepending on which command block you chose.)
Ctrl+Pick Block it.
3. Put 2 redstone blocks above the spawner.
4. Take out the first redstone block above the spawner then replace it with the command block.

Expected: Command to fire.

Happened: Did nothing on placement other then add the NBT.