Certificates of convenience and necessity and permits issued to motor carriers by state authorities under the authority of the laws of this state in effect prior to the date this chapter becomes effective shall remain in effect until confirmed, revoked or suspended by the commission, but persons who are the holders of such certificates and permits shall be subject to all provisions of this chapter. The procedure for confirming such certificates and permits shall be the same as is herein provided for issuing certificates and permits in the first instance: Provided, That if any common or contract carrier by motor vehicle of passengers, except by taxicab, was in operation on or prior to March 1, 1937, and any common or contract carrier by motor vehicle of property and of passengers by taxicab for hire was in operation on or prior to January 1, 1939, over the route or routes or within the territory for which application is made and has so operated since the respective dates, except as to interruptions over which the applicant has no control, the commission shall issue such certificate or permit without requiring further proof that the public convenience and necessity will be served by such operation and without further proceedings if application for such certificate or permit to operate is made to the commission within ninety days from the effective date of this chapter: Provided, however, That the applicant in the case of a common carrier or contract carrier by motor vehicle of passengers, except by taxicab, shall be required to submit proof of operation on or prior to March 1, 1937, and in the case of a common or contract carrier by motor vehicle of property and of passengers by taxicab, of operation on or prior to January 1, 1939, and continuously thereafter: Provided further, That pending determination of any application hereunder, the continuance of operation in which a common or contract carrier by motor vehicle of passengers, except by taxicab, was so engaged on or prior to March 1, 1937, and the continuance of operation in which any common or contract carrier by motor vehicle of property and of passengers by taxicab was so engaged on or prior to January 1, 1939, shall be lawful.