I'm sure almost anyone who's seen them in the store has seen eggs marked as 'vegetarian'. Now they may be chickens that are fed nothing but veggies, but I doubt it. More true to what they are is the 'Free-Range Vegetarian' tags on them, or at least the free range part. Chickens eat meat, naturally, in the wild they do. The pet chickens people have now a days eat meat still, my own birds have gone after snakes, mice, moles, small things like that they can get to. This is their choice as they free range and have 8 acres of land to roam on and eat all the grass they like. Every chicken owner will also agree their birds eat bugs; if they can get outside or if the bugs get in to the coop they'll eat them.
Why do I mention this? Because if you have a chicken that free ranges you will not stop them from going after bugs, or anything else they find tasty outside. Chickens can and will chase a bug at top speed across the ground till they catch it or the bug flies where they can't get. The minute that chicken eats that bug, that baby snake, anything like that it's not a vegetarian anymore, and no amount of talking to with a chicken will convince it not to eat something that's yummy (trust me I've tried.) So basically, if they free range, they are not vegetarian.
So what then if it just says 'vegetarian'? You have one very sick group of chickens if they're forced to be vegetarians. Chickens need protein to grow feathers, lay eggs, and be healthy chickens. Without a good source they can't do any of that, and if allowed chickens will start plucking one another's feathers and eating them to get protein, they can and will also attack, kill, and eat the weaker members of the flock. I am serious, this does happen, this is why most egg production chickens in plants have their beaks clipped. (I'm not going to get into how hens are treated in plants, you can google that if you want to.)
Basically you can't have real vegetarian chickens laying eggs, it simply wont happen. It's a good advertising ploy, but the reality is these eggs are not vegetarian.
Save yourself the money, get free range eggs. Or better yet get eggs from your local farmers markets. Most of the farmers there love their birds, and they probably treat them like pets. Sure the eggs may not be super pretty super market ones and they probably cost more but I can guarantee you the hens are happier and healthier then the ones that lay the store ones. (And remember what I've mentioned before, the healthier the hen, the healthier the egg.)
