The University of Wisconsin System came under fire Tuesday for spending $25 million in taxpayer and tuition dollars on a payroll system that may never materialize. Speaking at a state Assembly hearing, UW System leaders said they had taken steps to get an overhaul of the payroll system back on track after five years of mismanagement and $5 million in excess spending. They insisted that even “with its fits and starts,” the project “wasn’t too far off the mark in terms of time and cost.”