There will probably be an optoins to bake the ik on the import options in unity, you might have to do this by importing an actual maya scene, then unity will run maya in the bg to bake your animation.
If you only want to work with fbx and that option isnt working with fbx (it might do, if the script is clever enough to bake maya IK solvers to eular angles without launching maya), you need to bake out the IK animation before exporting your fbx.
FX supervisor - double negative