In 2005, them UFT President, Randi Weingarten badly miscalculated and agreed to eliminate seniority transfer, which allowed the DOE to impose school-based Fair Student Funding (fsf). Ms. Weingartem's miscalculation was that she didn't think that the DOE would allow ATRs to be without a classroom and pay 150 million dollars yearly. However, Chancellor Joel Klein and Mayor Michael Bloomberg believed it was worth the extra cost to eliminate veteran teachers and close schools while hiring inexpensive "newbies" in their "education on the cheap" policy. Of course Fair Student Funding did not affect the union leadership, only their rank and file members were affected by this perverse and discriminatory policy.
The main reason the union leadership didn't fight fsf is that they are not affected by the policy. Moreover, it doesn't hurt that they get double dues from the 1,300+ ATRs and the "newbies" hired by the schools in place of them. Finally, why should the UFT President, Michael Mulgrew, butt heads with his friend the Mayor? Better to have 1,300+ ATRs being glorified babysitters, with no right to refuse forced placements, than advocating for their placement back in the classroom and pissing off his buddy the Mayor.