No, what Blue Lava have is a service that still requiere of you that you have:
1)High speed (broadband) internet conection on the palces that you need to comunicate.
2)A ATA device. That is a device (little box) that converts from VOIP sent over the internet to normal phone line.
The ATA may be suplied as part of the service. You need to ask them
If you only need a interoffice conection, you only need the boxes, and the internet conection on both places.