Will monsters spawn in front of deactuated blocks?

[daimoth]

Let's say I've made all surfaces within spawning range unfit for mob spawning save one. Let's assume I'm preventing flying monsters as well. What happens if I actuate blocks atop that surface such that there are zero spawnable surfaces when the blocks are solid? Do they spawn as if the actuated blocks weren't there, provided they aren't solid at the time? Or will they not spawn at all in front of deactuated blocks, solid or not?