I've tried it just now, and there are no problems. I haven't used the Airbus supplied pushback.
Also, be sure you apply the latest Live update released yesterday, because it adds a new feature that recognizes the Airbus X Wheel chocks, so you can use them in place of the parking brakes. It's not really related to your issue, but it's best to update it anyway, because with one of the latest updates, it's possible to have the wheel chocks removing the parking brakes automatically, which conflicted with the GSX logic.