The engine driven hydraulic pumps are driven by the N2 section via the accessory gearbox. Therefore if the N2 has seized you will not have the pump. If the N2 is still windmilling you probably will still have the pump but it depends upon your IAS. At 300kts the N2 will stabilize at about 15% which should be enough.
If both engines have seized then start the APU for elecs to power the elec hyd pump.