I have to speculate since the article is short on molecular details, but I would guess the mosquitoes carry simple knockout mutations which prevent them from manufacturing some essential compound, maybe an amino acid.
Therefore, there's nothing of consequence to transfer to another species. You'd be transfering a gene that doesn't do anything.
Even if, in addition to transferring to another species, it somehow replaced the working gene in some individual, then the gene would simply die out due to the heavy selection pressure against it, leaving the rest of the population unharmed. (To counteract that with the mosquitoes, I take it fresh supplies of the engineered males are going to be repeatedly introduced?)
Therefore, there's nothing of consequence to transfer to another species. You'd be transfering a gene that doesn't do anything.
Even if, in addition to transferring to another species, it somehow replaced the working gene in some individual, then the gene would simply die out due to the heavy selection pressure against it, leaving the rest of the population unharmed. (To counteract that with the mosquitoes, I take it fresh supplies of the engineered males are going to be repeatedly introduced?)