Yes, they're compatible with HiPath 3000 V4 but I think it should be better to upgrade your whole system to HiPath 3000 V6 (upgrading your HG1500 V2 to HG1500 V3.0 too) to fully benefit from using (post-2006) optiPoint 4x0 V5 R4 software version.
Your HiPath 3000 V4 (with HG1500 V2...) should accept (pre-2007) optiPoint 4x0 V5 R1.35.0 software version at best (with NetBook 3.08 at best).
If you have SEBA Access you will find all the relevant Release Notes and Loadware files for your system's devices.
Best regards,
Kimera.