If it can, without expending reaction mass, that's what we want, whether we know how it works or not.
How fast is the “push” coming out of this thing? The speed of light? The point is to have an array that constantly fires when the object they are pushing is beyond a gravity well. Over time even the constant gentle push would push even a large mass to relativistic speeds...maybe not the speed of light since mass and velocity seem to have a relationship where mass becomes infinite at light speed unless space itself can be curved at the same time. Ionic propulsion works and they produce enough thrust over time to allow probes to catch up to comets at the velocities that they travel.