This act shall not alter, amend, repeal, modify or affect the laws of this state providing for the exercise of the power of eminent domain by public or quasi-public agencies, authorities and instrumentalities or by private persons, except as may be specifically provided herein and except that the power of eminent domain may be exercised to condemn and acquire airspace in the same manner as provided by law for the acquisition of other real property or for rights or interests in same. The procedure and rules provided by law for condemnation of real property by public or quasi-public agencies, authorities and instrumentalities and by private persons shall apply to the condemnation of airspace. Whenever more than one procedure for condemnation is provided by law and whenever there is doubt as to which procedure applies in a particular condemnation proceeding, the condemnation procedure applicable to the State Highway Commission or agency shall be followed.