Hey hankdaphoneguy,
Basically when vonage drops the lines off it comes off the customers high speed connection, vonage provides an interface that consists of rj11 outputs which would house your dialtones. You would simply take an rj11 line cord from their and punch it down on the trunk/line of the ksu.
Not sure if the company would have an IT person plugging these devices on the network they would also have username and password information to setup different vonage features via gui interface...for voicemail features etc.