in the uk they sell tequila with and without worms. if its in there, i'm thinking its generally added as its bottled, for the novelty factor, not as part of the fermentation process- i'd be dubious about the likelyhood of standardised looking worms showing up in all of the teeny tiny bottles otherwise.
i wanna see a letter from the manufacturers declaring whether or not the worms commited suicide while living a free, untortured life, before i'm prepared to drink anything with a worm actually in it. in a general store brand, if its not there in the bottle, i'd assume it never was there in processing either- why would they go to the hassle to add it, and then fish it out- it can't add a great flavour, can it- and if its a sales feature, why remove it?
tequila is a horrible drink anyway. gets you drunk from the legs up. nightmare stuff. i can also strongly advise against snorting it.