If the tenant pays rates, Net Assessable Value (NAV) is equal to the Assessable Value(AV) - rent received less a standard allowance of 20% for repairs and outgoings. If the owner is responsible for paying rates, rates paid can be deducted before allowing the 20% deduction. So, no further actual repair and renovation expenses could be deducted. And, no government rent could be deducted too.
Details in http://www.ird.gov.hk/eng/tax/ind_ppt.htm#06