I've been thinking hard about this... my interests are far beyond the spacetime dynamics, so even if there is say a "classical 'c' time delay, there still can be a "message" encoded in frequency modulation in gravitational waves. In line with your query, as well as the Star Trek type ideology, I wonder if you couldn't "warp" a magnetic field, in such a way to create gravitational waves, that would oscillate particles so that you could "receive" a message in the modulation of the resultant frequencies observed in the particles. I'm not familiar enough with the theoretical Alcubbiere warp physics, but common sense tells me if you can move mass through space, moving oscillations through mass through space to transfer information to distant objects should be trivial.