DES MOINES — A Senate subcommittee started work Wednesday on a massive property tax revamp that gradually would shift the cost of mental health services from Iowa’s 99 counties to the state and phase out the $152 million “backfill” to cities, counties and schools that was part of a 2013 compromise to replace local revenue lost when commercial and industrial property tax rates were cut by 10 percent.“We need to find a new way to fund this system,” said Sen.