Catalysis of the reaction: 1,5-bisdiphospho-1D-myo-inositol 2,3,4,6-tetrakisphosphate + H2O = 1-diphospho-1D-myo-inositol 2,3,4,5,6-pentakisphosphate + phosphate + H+.
inositol-1,5-bisdiphosphate-2,3,4,6-tetrakisphosphate 5-diphosphatase activity