In most parts of the country, 166.25 is an RP "Broadcast Auxiliary Remote Pickup" frequency, but in parts of the northeast (e.g.
PA,
NJ,
NY,
CT,
MA) it's been used for decades as a PW "Public Safety Conventional" freq, usually by fire departments.
I believe it's actually a federal frequency, and some licenses such as Bayonne NJ's, above, include the condition that "harmful interference will not be caused to Federal government stations."
EDIT: 166.25 and 170.15 (still used by KFI?) are covered in the NTIA Office of Spectrum Management
Red Book, section 4.1.3, "US11 - On the condition that harmful interference is not caused to present or future Federal stations in the band 162-174 MHz, the frequencies 166.25 MHz and 170.15 MHz may be authorized to non-Federal stations, as follows:
(1) eligibles in the Public Safety Radio Pool may be authorized to operate in the fixed and land mobile services for locations within 150 miles (241.4 kilometers) of New York City; and
(2) remote pickup broadcast stations may be authorized to operate in the land mobile service for locations within the continental United States, excluding
· Alaska
· locations within 150 miles of New York City, and
· the Tennessee Valley Authority Area (TVA Area)."