Section 18J. Beginning July 1, 2009, any new or substantially renovated multi-line telephone system shall provide the same level of enhanced 911 service that is provided to others in the commonwealth. The department shall adopt regulations to implement this requirement. In such regulations the department may exempt certain multi-line telephone systems from this requirement based on such factors as costs and the public benefits of compliance, except that accessibility of such a system to people with disabilities may only be waived if the proponent of the waiver has shown it to be technologically infeasible or of excessive cost without benefit to the disability community. For the purposes of this section, a “multi-line telephone system” shall mean a system comprised of common control units, telephones and control hardware and software providing local telephone service to multiple end-use customers in businesses, apartments, townhouses, condominiums, schools, dormitories, hotels, motels, resorts, extended care facilities, or similar entities, facilities or structures. “Multi-line telephone system” shall include: (1) network and premises based systems such as centrex, pbx and hybrid key telephone systems; and (2) systems owned or leased by governmental agencies, nonprofit entities and for-profit businesses.