If the equipped monster’s ATK is raised above 1000 points, by any effect other than "Buster Rancher"’s own effect, "Buster Rancher" is destroyed.
You can equip 2 copies of "Buster Rancher" to the same monster but because of "Buster Rancher"’s effect, when you increase the ATK by 1 "Buster Rancher" effect, the other "Buster Rancher" is destroyed.
If "Injection Fairy Lily" is equipped with "Buster Rancher", and you use her effect to increase her ATK, "Buster Rancher" is destroyed. If "Injection Fairy Lily" battles a monster equipped with "Buster Rancher", and her effect is used to increase her ATK, then "Buster Rancher"’s effect activates and increases the ATK of the other monster.