There's two parts to this reply. Read on.
About the outlets specifically, I am pretty sure they're only using the one repeater on DMR and that's it. Since they're using DMR, it's kind of pointless to have any analog frequencies. The stores themselves likely use several analog low power walkie-talkie frequencies.
The second part of the reply is about searching. You seem willing to do the leg work to find what you're looking for. And honestly that is becoming rare. People just want to log in and get spoon fed the information. But 100% of the information in
Radio Reference,
Scan New England and others are completely determined by people doing the legwork in those areas, searching, listening; doing the detective work to get the info. Fewer people are doing it, and those that have been for 20-30 years or more are getting tired of being the only ones.
Below are the FCC sites pertaining to where pretty much all voice lives. It's not the only bands. There is Broadcast (within VHF & UHF), 800Mhz, 900Mhz, etc. But this is where it usually happens. If you look at the frequencies in the pools, read the conditions, etc. you can begin to understand the landscape of voice radio communications.
a couple hints: Public safety is typically licensed, business doesn't always bother. Some use FRS & GMRS frequencies for business.
47
CFR Part 90 Public Safety Pool
47
CFR Part 90 Industrial/Business Pool
47 CFR Part 95 Personal Use Radio Systems (I.e. FRS, GMRS, MURS, etc)
FCC General Menus Report (FCC Licenses)
In the short term, on the slim chance the outlets are using anything else, search between 450-470Mhz. Feel free to shoot me a PM if you have any questions.