A319 CREW MADE A WRONG TXWY TURN ON TAXI OUT; AND GOT AHEAD OF A B727 AT PHL DURING NIGHT; LOW RVR; SNOW OPS.

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AFTER DEICING IN PHL; WE TAXIED SBOUND OUT OF THE DEICE PAD FOR DEP. WE CONTACTED PHL GND CTL AND RECEIVED CLRNC (AND READBACK) TO TAXI TO RWY 9L VIA TXWY S AND TXWY Y. VISIBILITY WAS VERY RESTR DUE TO THE SNOW FALLING (1/2 SM RWY 9R 1800/2800 RVR). WE COULD NOT SEE THE TWR AND THEY COULD NOT SEE US. I DO NOT BELIEVE THE PHL TWR HAS GND RADAR TO TRACK TAXIING ACFT. THIS WAS THE CAPT'S FIRST TIME DEICING IN PHL AT THIS NEW PAD LOCATION. POST DEICE IS A VERY BUSY TIME FOR THE FO AS WELL (ENTERING PERFORMANCE; DOING BEFORE TKOF CHKLIST; REMAINING SITUATIONALLY AWARE; WORKING RADIOS). THE CAPT TAXIED N ON TXWY Y TO RWY 9L AT TXWY K6. ACFT USUALLY ARRIVE RWY 9R AND DEPART RWY 9L AT PHL IN THE E CONFIGN. ARRS ON RWY 9L AND DEPS ON RWY 9L ARE UNUSUAL. RWY 9R WAS BEING PLOWED. WE SAW NO ILS HOLD SHORT SIGNAGE OR PAINT OR LIGHTS AS WE PASSED THROUGH THE APCH GLIDE PATH FOR RWY 9L ON OUR TAXI N. WE DIDN'T REALLY THINK ANYTHING OF OUR POS (N OF RWY 9L) UNTIL TWR TRIED TO SEQUENCE A B727 AHEAD OF US FOR DEP (WE WERE NOW BLOCKING). THE LCL CTLR SEEMED CONFUSED THAT WE WERE N OF RWY 9L AND NOT STILL S OF THE ACTIVE. WE HADN'T CROSSED ANY RWYS BUT WE DID CROSS THE EXTENDED CTRLINE OF RWY 9L. OUR CONCERN IS THAT WE MIGHT HAVE DISRUPTED ILS SIGNALS FOR ARRIVING ACFT OR; MORE IMPORTANTLY; BLOCKED THE APCH GLIDE PATH OF OTHER ARRIVING ACFT. NO OPERATIONAL PROBS OCCURRED. WE WERE SEQUENCED FOR DEP AND NO OTHER CONTACT FROM THE TWR OR COMPANY WAS RECEIVED ABOUT THE MATTER. NO ILS HOLD BAR MARKINGS APPEAR ON OUR PHL ARPT COMMERCIAL PAGES FOR TXWY Y AND ANY SIGNS OR PAINT THAT MIGHT EXIST WERE POSSIBLY COVERED BY SNOW. IN ANY EVENT; THIS FLC DIDN'T SEE THEM.