Here's a theory - I don't know anything about the area in question, but he keeps mentioning that it's a "repeater" number. Could it be that certain repeaters have certain CTCSS/PL codes enabled? Here, the police have multiple sites hey can access, which they know as a letter-number combination. For example, B2 and B7 are the same frequency but two different PLs, 123.0 and 131.8. So a regular user of the system might know it as simply "B2" or "B7". Or, in this case, "repeater 12".
If that makes sense, then the issue stands - the original poster needs to figure out what repeater site 12's properties are. There must be a PL code or something similar in there.
EDIT: After looking at the link posted above, I stand corrected - yes, it is the PL code as listed on that website. I concur that "12" = 100.0.