The Taco Bell beans are vegetarian; they're made with vegetable shortening. However, the bean burrito may come into contact with non-vegetarian items as it's being prepared.
Taco Bell bean burritos are vegetarian--completely lard free--and if you order it "fresco", it's also vegan. The same goes for just about every other "bean" product they offer.
The Taco Bean bean burrito is made of 100% non meat ingredients, as far as I know. I doubt they use lard, as that would not give them a substantial taste they already have.
When I worked there we pressure cooked the pinto beans in these large pots for hours I remember adding water but I don't remember adding anything else to the beans.
