Airbus have the 'Soft Limit" philosophy, they think if you really need to bbreak a limit for safety reasons, you can do so. Wheras I gather the only Boeing FW aircraft, the 777 has hard limits.
If you pitched down 10 degrees as you mention, the aircraft will raise the nose as you get to VMO. Further forward pressure on the sidestick will allow you to exceed it, but you have to hold the pressure - and you will have the overspeed warning going off. The system will not allow you to exceed the design limits. From memory of trying it in the simulator, you can get to about 385 knots before it stops you pitching any further, 35 knots above VMO.