Each residential property is exempted from the CPA surcharge for the first $100K of value. Each resident is also entitled to exemptions from the CPA surcharge if they qualify for low income housing or low and moderate senior housing exemptions. The Community Preservation Coalition has information on implementing CPA which includes information on how the low and moderate income exemptions work.
A description of how this works is available. Basically the town sends out information outlining exemption income eligibility and the resident fills out a standard abatement form that is available from the DOR.