My dad does a lot of cooking and he buys chicken broth from Costco by the cases. He uses it to floavor lots of things. I never realized it until I got married and tried to watch him so that I could try to cook like him (still can't, but my brother tells me that my meatballs are good!)
I know that it is a popular way to make mashed potatoes, instead of using milk and butter.
It's probably best to ask and alert your server that you are vegeterian. I am sure that they can have the food prepared for you the way you request.