For purposes of RCW 85.05.610 through 85.05.650:

(1) The word “owner” as it appears in chapter 85.05 RCW shall include the owner of any undivided interest in any tract of land within the district boundaries, whether Indian trust land or restricted land, or non-Indian land;

(2) The “acreage” owned by any owner in any undivided estate interest shall be computed by multiplying the owner’s fractional undivided interest against the total acreage embraced within a particular tract or lot assessed; and

(3) The names of the owners of Indian lands, the size of Indian tracts and lots, the fractional undivided interest therein and the “acreage” of each owner as determined according to the provisions of subsection (2) of this section shall, in any proceeding to organize and operate a district under the provisions of RCW 85.05.610 or pursuant to any other provision of chapter 85.05 RCW as now or hereafter amended, be conclusively determined by the certificate of the superintendent of the Indian agency of the Bureau of Indian Affairs having supervision over the Indian reservation in which such Indian lands may be located or by the certificate of the area director over the Bureau of Indian Affairs area encompassing such lands; and such certificate shall be accepted in lieu of all other evidence in the records of the county in which such lands are situated.