How much could passing a fatwa do? Apart from causing anger in certain quarters, other than that it will not do much. Just a declaration that Muslim clerics do not condone the manner in question. Lesbians are not only caused by women who cross dresses and adopt mannerism of a man. It is more psychological than just skin deep.
Instead of releasing Fatwas on this and that why not go out there and do some sort of education campaign and create awareness? Releasing a Fatwa does and will not change anything much apart from raising the anger of some activists which more often than not have no knowledge of what Islam is and should be.
This is where practices in society does not conform to religious beliefs and the only way to curb and eradicate the problem is trough education. To start things off why not concentrate at colleges and universities. That is normally where these things start. So stop going on about the Fatwa and really act on it.