(j) To undertake as a separate project the renovation, remodeling, reconstruction, repair, landscaping and improvement of an existing housing project or part thereof, including the reduction of undesirable unit densities in an existing housing project as deemed necessary by the department for the improvement of an existing housing project assisted by the commonwealth pursuant to section thirty-four or forty-one; provided, that an equal number of low-rent relocation units are provided to replace those occupied units which are removed in the reduction of an undesirable unit density; and provided, further, that the plans for each such project shall be undertaken in accordance with rules and regulations promulgated by the department for such projects; and provided, further, that notwithstanding the provisions of any other law, where the funding for such project or any similar state or federally funded undertaking with respect to low-rent housing exceeds fifteen million dollars, the number of households living on the original site when funds are or were committed exceeds two hundred and a receiver has been appointed for the housing authority pursuant to section one hundred and twenty-seven H of chapter one hundred and eleven, the award of construction, reconstruction, installation, demolition, maintenance, alteration, remodeling or repair contracts shall be governed by the provisions of section thirty-nine M of chapter thirty, and shall include a requirement for certification of ability to furnish labor that can work in harmony with all other elements of labor employed or to be employed in the work, and shall not be subject to the provisions of sections forty-four A to forty-four H, inclusive, of chapter one hundred and forty-nine; and provided, further, that