I'm not sure that this is still accurate, but according to the Jeppesen 10-9 Airport Diagram I have for KBOS(Revision date Jul 30, 1999):
121.9 is GROUND
121.75 is for HELICOPTER
Additional freqs are:
D-ATIS 135.0
CLEARANCE DEL 121.65
GATE CONTROL 134.05
TOWER for RWYS 4R/22L and 9/27 119.1
TOWER for RWYS 4L/22R, 15L/R, and 33L/R 128.8
DEPARTURE 133.0
This mentions no East/West division, and only gives one freq for GROUND...but like i said...this Jepp is from 1999! Hope this helps!
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