I've talked to a number of people who have tried reparative therapy, and it's a topic that's been explored by a number of gay JWs. None of them have resulted in a gay-to-straight switch. The gay JW support group actively discourages its members from undergoing it as they've concluded that it's mentally harmful. Being celibate for your faith is one thing, but imposing active heterosexuality is another, one that can have unfortunate consequences:
http://www.guardian.co.uk/commentisfree/belief/2009/aug/15/gay-religion-acceptance-judaism
And it's not like there aren't compelling reasons, faith aside, to conform to the heteronormative:
http://news.bbc.co.uk/1/hi/world/middle_east/8204853.stm
If that sort of persecution doesn't make you straight, will a chat and hug with a tubby, bearded counsellor be any more successful?