Billerica leaders must decide whether to press forward with plans to renovate the town's historic center ­after voters at Monday's special election rejected an ambitious $14 million proposal to update sidewalks, sink utility wiring underground, and reroute traffic.    

 The landmark vote brought 40 percent of the town's 26,217 registered voters to the polls, more than double the percentage that typically turns out for local elections, said Town Clerk Shirley Schult. The referendum marked the first time in Billerica's ­recorded history that a proposal ­approved at Town Meeting was rejected by a townwide vote.