DRG ARR, PLT ACKD RCPT OF ATIS INFO & FLD COND RPRT, BOTH IN DCG BRAKING ACTION "FAIR TO POOR." HE WAS NOT ADZD OF 3 PLTRPRTS OF BRAKING ACTION "POOR TO NIL" OR "POOR." ACFT WAS CLRD FOR VOR/DME APCH TO RWY 15R. DUE TO PSBL WND SHEAR, 35 DEG OF FLAPS (INSTEAD OF 50) WAS EXTDD DRG APCH. AUTOTHROTTLE/SOD CTL (AT/SC) WAS USED TO CTL SPD (APRX 10 KT HI) DRG APCH. THE HIGHER SPD WAS ACCEPTED IAW CO SOP, BUT THE AT/SC WAS USED THRU-OUT THE FLARE. THE ACFT TCHD DWN APRX 2500' BYD THE DSPLCD THRESHOLD WITH ABOUT 6690' RMNG. (NO LGTD RWY DSTC MKRS AVBL.) ALL DCLRTV DEVICES WERE USED TO SLOW THE ACFT, BUT IT CONTD BYD END OF RWY & WENT OVR A SEA WALL. INV REVEALED PRECIP HAD RFZN TO FROM GLAZE ICE. OF 14 PLTS, 9 HAD NOT VOLUNTEERED BRAKING ACTION RPRTS & TWR DID NOT ASK FOR RPRTS DRG CONTD PRECIP. ATIS NOT UPDATED FOR 2 HRS. FAA REGS LACK GUIDANCE TO ARPT MNGMNT FOR MEASUREMENT OF RWY SLICKNESS, LACKED MEANS OF CORRELATING SLICK RWY SFC WITH ACFT STOP DSTC, DID NOT EXTD AUTH RWY LENGTHS FOR ICY RWYS. ARPT MNGMNT DID NOT INSP/IMPROVE RWY COND AFT BRKG RPRTD POOR/NIL