I don't know, if any, agencies that can use a particular frequency without the FCC knowing about it.
Try searching the FCC General Menu Reports for the new MOSWIN frequencies of 152.600 or 152.660.
You will not find anything yet those are the control channels for the Weldon Spring and Imperial, MO sites.
Also try 148.600. It will also not produce any results. Yet Missouri uses it pretty much statewide for their mobile extenders.
The same is true for most of the frequencies that the federal government has allowed states to use. Those type frequencies are not assigned or controlled by the FCC so they won't normally show up. There are actually a lot of them in use across the country that will not show up in an FCC search.
The two 152.xxx ones I listed first are FCC allocated frequencies but they are for a market area and handle paging. Missouri managed to get an exception to use them in some areas of the state for MOSWIN. I think those are frequency blocks assigned to a bidder in an auction so only the entire block will show up and then they are further broken down into geographic market areas. So a search on those will usually only reveal the market area and who owns or controls that area. I don't know how but I bet there is a way to drill into these market area type frequencies and determine actual transmitter locations with geo info. If anyone knows how that is done, please advise as I'd love to be able to determine actual locations of the MOSWIN sites that use the paging or fed frequencies. I know that info is listed here but there are going to be times it is not listed here and I have no idea how to find it myself so if someone knows that would be a big help.
Searching the FCC site is not nearly as accurate or as easy as it was before. There are ways to find the info from applications the state made but the normal General Menu Reports search will not show the actual users of the paging market areas. It will only show who the market area owner is.
I'm not sure about the federal frequencies in use today for state public safety. I assume one could still find info from FCC applications on those frequencies also but its a tad more work finding what you are after. Even if you know the callsign for a site that is assigned frequencies in the federal ranges or the special market areas like the Part 22 (I think) paging markets, a callsign search often does not reveal very much info such as location detail and even all the freqs associated with that callsign.
Here's the link for the primary FCC search site that is usually very handy for the scanner listener:
FCC General Menu Reports 3.1.14 October 7, 2010
All the ones I listed above will show up in a search here at RR though as users have submitted them!
I also found the database here for the STL City P25 South Patrol tower does not agree at all with what is found at the FCC. The FCC says the site does not exist. I've asked in the Missouri forum if anyone can confirm that the South Patrol 700 MHz site is even on the air but nobody has confirmed yes or no. I know it went off the air well over a year ago and then not long back I saw a post stating it was back on the air. I tried it and cannot get a hint of a signal at all where before when it was on the air, I could receive that site but not near as well as the main North Patrol site which is actually a citywide simulcast site. I never figured out where the names of South and North Patrol sites came from as the North Patrol was the original and only site. The South Patrol site was added later and never had hardly any traffic on it. What traffic was on the South Patrol site was also carried by the North Patrol site at the same time. I think the North Patrol site should be renamed as City Main and if there is a south patrol site, it should be called South Site backup or something as it never carried all the south traffic. Only a few cars had 700 MHz radios.
With the city changing from 9 to 6 districts, something very well could change but I doubt they will split up the radio systems.