Got these from Baton Rouge Area Scanning's Website:
Mutual Aid Frequencies - Non-Trunked Frequencies on Trunked System: The Federal Communications Commission (FCC), in Docket 87-112, Sec. IV.C.50-52, released Dec. 18, 1987, mandated the use of a single, conventional, common-calling channel and four (4) tactical channels on a nationwide basis in the new 800 MHz Public Safety allocations. The FCC also strongly recommended the use of CTCSS tone squelch nationally on a frequency of 156.7 Hz. These "Mutual Aid" frequencies are as follows:
866.0125 Calling
866.5125 TAC1
867.0125 TAC2
867.5125 TAC3
868.0125 TAC4