Seth at In Effect nailed it -- County Exec Scott Walker bet on beating the union and lost. Seth is likely absolutely right that county officials did not want to testify under oath. It was clear that the potential layoffs were the club the Walker Administration and county supervisors wanted to use to beat the union into submission. They were pretty open about that.
It is also entirely conceivable that Walker did not want the errors made by his administration in calculating costs and relying on unreliable consultants to get the attention that public testimony would bring. Walker thought he would have an easy knockout in the 15th round. Instead, he is flat on his back on the mat, and the boot of AFSCME District Council 48 is planted hard -- with spikes -- on his chest.