I have found that via set block command that custom spawners do not work. This issue can be replicated by placing a command block and I specifically used "/setblock ~ ~1 ~ minecraft:mob_spawner 0 replace {EntityId:Zombie}" without quotations of course to see if it would spawn via set block command and it only spawned a pig spawner instead of a zombie spawner. Video link included to show bug https://www.youtube.com/watch?v=9vvB9FDtQkQ&feature=youtu.be
Environment
Operating System: Windows 10
Processor: Intel Core i7-4500U CPU @ 1.80GHz 2.40GHz
System Type: 64-Bit Operating System, x64 Based Processor
Java Version: 1.8.0_51
The EntityId tag as been removed