yes, you can, but it involves removing your POTS lines from your telephone 'trunk' (probably in your supers electrical room).
The POTS lines are what powers your phone with electricity, so they have to be removed. The Motorola ATA device from Vonage can power ~3-5 devices (aka phones), as a limit.
However, removing the POTS lines will probably kill your buzzer. So you'll have to choose one or the other.