Bronxville union contract limits health insurance* provider choices to two

According to this report, the Bronxville school district union contract allows for only two possible health insurance* providers, with one of those being an excessively costly option according to the state Comptroller's office.  Why limit choices to only two?

The state Comptroller’s office has released its audit of the Bronxville school’s spending during the 2009-10 school year, finding only one place where money could have been saved: health care.
The audit looked at health insurance benefits from July 1, 2005, through July 31, 2010, and determined the district could have saved about $1 million in the past three years if it had pulled out of a statewide consortium and found a cheaper plan on its own.
The district, in its response, said pulling out of the consortium would have cost $1.2 million in unrecoverable fund balance payments over the past three years and would have violated union contracts, which specifically named the consortium as one of two insurance providers.
However, the district said it would continue to monitor the consortium’s fund balances and demand repayment where applicable, and seek a seat on the consortium’s board of directors to increase oversight. The district also said it would continue to monitor its health care options to make sure it chooses the most cost-effective of the appropriate coverage options.

http://reviewpress.lohudblogs.com/2011/02/23/state-audits-bronxville-schools-healthcare-costs-could-be-less/

* Corrected