(a) Cases subject to arbitration Except as provided in (b), the following cases must be arbitrated: (1) In each superior court with 18 or more authorized judges, all unlimited civil cases where the amount in controversy does not exceed $50,000 as to any plaintiff; (2) In each superior court with fewer than 18 authorized judges that so provides by local rule, all unlimited civil cases where the amount in controversy does not exceed $50,000 as to any plaintiff; (3) All limited civil cases in courts