Okay, so FTB does mess with spawners a bit. First, we need to establish what pack you are on. If you are on Beta Pack A, then it has the Portal Gun mod, if you are on Magic World it has Soul Shards (I think) and Mindcrack has Soul Shards and Portal Gun may be added although it has had a complete rewrite.
If you have the Soul Shards mod, it basically allows you to create your own spawners of any mob.
Here's a link to the MCF thread:
http://www.minecraftforum.net/topic...v114-and-recipe-remover-v11-updated-12222012/
If you have the Portal Gun mod, by pointing the portal gun at a block and pressing your G key, it will pick it up similar to the way you can pick up Safety Cubes in the Portal series, and then you can press G to place it down elsewhere. This feature may have been nerfed in the rewrite, I'm not sure.
This documentation has info for the previous version (the one in Beta Pack A and Magic World)
http://www.minecraftforum.net/topic/199391-146smpforge-portal-gun-reconstructed-v1-rewritten-again/
As far as I know, there is nothing else that uses spawners in any special way in the current FTB packs.
EDIT: Added Portal Gun link
EDIT 2: Portal Gun is not in Magic World